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CHAPTER
42 BIRDSPlanning Guide
Compression GuideTo shorten instructionbecause of time limitations,omit Section 1.
Chapter Opener
Section 1 Origin and Evolution of Birds• Identify and describe seven major characteristics
of birds.• List three similarities between birds and dinosaurs.• Describe the characteristics of Archaeopteryx.• Summarize the two main hypotheses for the evolution
of flight.
Section 2 Characteristics of Birds• Describe the structure of a contour feather.• Identify two modifications for flight seen in a bird’s
skeletal system.• Contrast the function of the gizzard with that of the crop.• Trace the movement of air through the respiratory system
of a bird.• Explain the differences between altricial and
precocial young.
TE Activity Lift, p. 844 ◆gTE Activity Bone Density, p. 845 ◆gSE Quick Lab Comparing Wing Structures,
p. 845 ◆gANC Datasheets for In-Text Labs Comparing Wing
Structures*gTE Activity Bird Heart Model, p. 847 ◆aTE Group Activity Bird Songs, p. 848 ◆aSE Exploration Lab Comparing Feather Structure and
Function, pp. 858–859 ◆gANC Datasheets for In-Text Labs Comparing Feather
Structure and Function*gHBS Quick, Data, and Math Labs Calculating Average
Bone Density*g
TE Demonstration Bird Feet, p. 851 ◆bTE Internet Activity Classification of Birds,
p. 851 gTE Activity Observing Wild Birds, p. 853 ◆aTE Activity Birdhouses p. 853 ◆g
HBS Skills Practice Labs Conducting a Bird Survey* ◆g
OSP Parent LetterCD Student Edition on CD-ROMCD Guided Reading Audio CD
TR I23 Characteristics of Birds*TR I24 Phylogenetic Diagram of Birds,
Reptiles, and Mammals*
TR I25 External Structure of Birds—Bald Eagle*
TR I26 Internal Structure of Birds—Bald Eagle*
TR I27 Contour Feather Structure*TR I28 Avian Skeleton*TR I29 Avian Heart Structure*TR I30 Avian Lung Structure*CD Visual Concepts CD-ROMCD Virtual Investigations Respiration
in Vertebrates
TR I31 Avian Adaptations*CD Visual Concepts CD-ROM
pp. 840–843
840A C H A P T E R 4 2 B i r d s
OBJECTIVES LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCESPACING • 45 min
pp. 844–850PACING • 90 min
pp. 851–854PACING • 45 minSection 3 Classification• Describe the relationship between beak shape and
diet in birds.• List 10 major orders of living birds, and name an example
of each order.• Describe the function of the syrinx.
TE Demonstration Birds and Turtles, p. 841 ◆bTE Internet Activity Birds, p. 842
SE Chapter Highlights, p. 855SE Chapter Review, p. 856TR Graphic Organizer*gTR Concept Mapping*g
ANC Vocabulary Review*gANC Quizzes*gANC Chapter Test*gANC Chapter Test*a
SE Standardized Test Prep, p. 857OSP Test GeneratorOSP Test Item Listing
CHAPTER REVIEW, ASSESSMENT, ANDSTANDARDIZED TEST PREPARATION
PACING • 90 min
Visit go.hrw.com to find avariety of online resources.Click Holt Online Learningfor an online edition of this textbook and otherinteractive resources.
This DVD package includes: • Holt Calendar Planner• Customizable Lesson Plans• Editable Worksheets• MindPoint® Quiz Show• Holt PowerPoint® Resources
• ExamView® Version 6.0Assessment Suite
• Interactive Teacher’s Edition• Holt PuzzlePro®
Online and Technology Resources
KEY SE Student Edition OSP One-Stop Planner VID Classroom Video/DVDTE Teacher Edition TR Transparencies and * Also on One-Stop Planner
ANC Ancillary Workbook Transparency Worksheets ◆ Requires advance prepHBS Holt BioSources Lab Program CD CD or CD-ROM
TE Using the Figure Characteristics of Birds, p. 840ANC Science Skills Worksheet*gANC Critical Thinking Worksheet*a
TE Reading Skill Builder Interactive Reading, p. 841 bTE Inclusion Strategies, p. 842TE Skill Builder Interpreting Visuals, p. 843 g
ANC Active Reading Guide*
TE Using the Figure Bird Stomach, p. 846 gTE Reading Skill Builder Active Reading, p. 847 gTE Eco Connection, p. 848TE Reading Skill Builder Vocabulary, p. 849 bTE Skill Builder Science Literacy, p. 849 a
ANC Active Reading Guide*
TE Reading Skill Builder Reading Organizer, p. 851 bTE Skill Builder Science Literacy, p. 852 ◆gTE Inclusion Strategies, p. 852TE Using the Figure Adaptive Advantage, p. 853 a
ANC Active Reading Guide*
TE Assessing Prior Knowledge, p. 840ANC Study Guide*g
SE Section Review, p. 843 gTE Reteaching, p. 843 bTE Quiz, p. 843 g
SE Section Review, p. 849 gTE Reteaching, p. 849 bTE Quiz, p. 849 g
SE Section Review, p. 854 gTE Reteaching, p. 854 bTE Quiz, p. 854 gTE Alternative Assessment, p. 855 gTE Study Tip, p. 855 g
National Science EducationStandards
LSEvol1, UCP1, UCP2, UCP3, UCP4
LSMat4, LSBeh2, UCP5, SI1, SI2
UCP1, UCP2, UCP5
C H A P T E R 4 2 P l a n n i n g G u i d e 840B
SKILLS DEVELOPMENT RESOURCES REVIEW AND ASSESSMENT CORRELATIONS
Maintained by the National ScienceTeachers Association.
www.scilinks.orgClassroom CD-ROMs
• Guided Reading Audio Program• Student One Stop• Virtual Investigations• Visual Concepts• Dissection Labs
Classroom Videos
• Lab Videos demonstratethe chapter lab.
Holt Lab GeneratorCD-ROM
Search for any lab by topic, standard,difficulty level, or time. Edit any lab to fit your needs, or create your own labs.Use the Lab Materials QuickList softwareto customize your lab materials list.
840 C H A P T E R 4 2
CHAPTER 42Using the FigureCharacteristics of Birds Ask students to study the young owlclosely. Ask them to name theexternal characteristic that setsbirds apart from other animals.(Birds have feathers.) Tell studentsthat some dinosaurs may alsohave had feathers, but no otherliving vertebrate possesses these structures. If students answer“wings,” remind them that batsand many arthropods also havewings. If they answer “beaks” or“bills,” remind students that otheranimals have similar structures.For example, some cephalopodshave beak-like structures, andplatypuses have bills. Visual
Assessing PriorKnowledgeReview the following conceptswith students.
Cellular Respiration (Ch. 7): Askstudents how birds generate theenergy necessary to fly. (They havea very high metabolic rate.) Then askwhat structures prevent heat fromescaping from a bird’s body oncold days. (feathers)
Reptiles (Ch. 41): Ask studentsto name some characteristics ofsome dinosaurs that can be foundin birds today. (flexible, S-shapedneck; unique ankle joint; hollow bones)
GENERAL
LS
Standards Correlations
National Science Education Standards
LSEvol1 Species evolve over time.
LSMat4 The complexity and organization of organismsaccommodates the need for obtaining, transforming, transporting, releasing, and eliminating the matter andenergy used to sustain the organism.
LSBeh2 Organisms have behavioral responses to internalchanges and to external stimuli.
UCP1 Systems, order, and organization
UCP2 Evidence, models, and explanation
UCP3 Change, constancy, and measurement
UCP4 Evolution and equilibrium
UCP5 Form and function
SI1 Abilities necessary to do scientific inquiry
SI2 Understandings about scientific inquiry
Young birds, such as this owl, depend ontheir parents for food and protection.
SECTION 1 Origin and Evolution of Birds
SECTION 2 Characteristics of Birds
SECTION 3 Classification
42CHAPTER BIRDSBIRDS
Biology Virtual InvestigationsRespiration in Vertebrates
840
B I R D S 841
OverviewBefore beginning this section,review with students the Objectives listed in the StudentEdition. This section describesavian evolution, key bird charac-teristics, and hypotheses on theorigins of flight.
Bring a feather to class and hold it up for students to see. Ask them what kind of animal hasfeathers. (a bird) Most studentswill answer correctly. Ask studentsto think of a living animal that hasfeathers but is not a bird. (Thereare none) Stress that feathers arethe key characteristic of birds.
Logical
DemonstrationBirds and Turtles Show studentsa live turtle or a picture of a turtle.Ask students what readily visiblecharacteristics of the turtle arealso found in birds. (beak, scales,and claws) Visual
Interactive Reading AssignChapter 42 of the Modern BiologyGuided Reading Audio CDProgram to help studentsachieve greater success in reading the chapter.
VerbalLS
SKILLBUILDER
READINGREADING
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SECTION 1
OR I G I N A N D E VO L U T I O N
O F B I R D SBirds belong to the class Aves, which, with nearly 10,000 species,
is the largest class of terrestrial vertebrates. Birds are also the
most recently evolved group of vertebrates, having appeared
only about 150 million years ago. Among living vertebrates,
only birds and bats can fly. The bodies of most birds are well
adapted to flight.
CHARACTERISTICSAlthough there are many kinds of birds, birds are so distinctivethat it is difficult to mistake one for any other kind of vertebrate.All birds—even those that cannot fly—share the seven importantcharacteristics described below.• Feathers—Feathers are unique to birds, and all birds have them.
Like hair, feathers are composed mainly of the versatile proteinkeratin. Feathers are essential for flight, and they insulate abird’s body against heat loss.
• Wings—A bird’s forelimbs are modified into a pair of wings.Feathers cover most of the surface area of the wing.
• Lightweight, rigid skeleton—The skeleton of a bird reflects therequirements of flight. Many of the bones are thin-walled andhollow, making them lighter than the bones of nonflying animals.Air sacs from the respiratory system penetrate some of thebones. Because many bones are fused, the skeleton is rigid andcan resist the forces produced by the strong flight muscles.
• Endothermic metabolism—A bird’s rapid metabolism suppliesthe energy needed for flight. Birds maintain a high body tempera-ture of 40–41°C (104–106°F). The body temperature of humans,by contrast, is about 37°C, or 98.6°F.
• Unique respiratory system—A rapid metabolism requires anabundant supply of oxygen, and birds have the most efficientrespiratory system of any terrestrial vertebrates. The lungs areconnected to several sets of air sacs, an arrangement thatensures that oxygen-rich air is always in the lungs.
• Beak—No modern bird has teeth, but the jaws are covered by atough, horny sheath called a beak.
• Oviparity—All birds lay amniotic eggs encased in a hard,calcium-containing shell. In most species, the eggs are incubatedin a nest by one or both parents.
SECTION 1
O B J E C T I V E S
● Identify and describe seven majorcharacteristics of birds.
● List three similarities between birdsand dinosaurs.
● Describe the characteristics ofArchaeopteryx.
● Summarize the two mainhypotheses for the evolution of flight.
V O C A B U L A R Y
furcula
841
STATE RESOURCES
For specific resourcesfor your state, visitgo.hrw.com and type inthe keyword HSHSTR.
TEACHER RESOURCES
Workbooks
Active Reading Guide (Section 1)
Technology
Transparencies• I23 Characteristics of Birds
Visual Concepts CD-ROM• Characteristics of Birds
842 C H A P T E R 4 2
EVOLUTIONThere are many similarities between birds and some dinosaurs,such as Caudipteryx show in Figure 42-1. Three of these similaritiesinclude a flexible S-shaped neck, a unique ankle joint, and hollowbones. Birds are thought to have evolved from small, fast-runningcarnivorous dinosaurs during the Jurassic period (200–146 millionyears ago). Figure 42-1 shows the likely relationships betweenbirds and other terrestrial vertebrates.
The oldest known bird fossils are classified in the genusArchaeopteryx and date from the late Jurassic period, about 150million years ago. In the fossil in Figure 42-2a, the shapes of feath-ers are clearly visible. Feathers covered Archaeopteryx’s forelimbs,forming wings, and covered its body and tail as well. Like modernbirds, Archaeopteryx had hollow bones and a furcula(FUHR-kyoo-luh), the fused pair of collarbones commonly called awishbone. The furcula plays an important role in flight by helpingto stabilize the shoulder joint. Based on such similarities with mod-ern birds, scientists think that Archaeopteryx could fly. However,Archaeopteryx also had several characteristics of its dinosaurancestors, including teeth, claws on its forelimbs, and a long, bonytail. Figure 42-2b shows an artist’s conception of what anArchaeopteryx might have looked like.
Origin of FlightThe evolution of a flying animal from nonflying ancestors entailsmany changes in anatomy, physiology, and behavior. According toone hypothesis, the ancestors of birds were tree dwellers that ranalong branches and occasionally jumped between branches andtrees. Wings that allowed these animals to glide evolved. Once glid-ing was possible, the ability to fly by flapping the wings evolved.
This phylogenetic diagram represents ahypothesis for the relationship amongbirds, reptiles, mammals, and someextinct relatives of birds. For updateson phylogenetic information, visitgo.hrw.com. Enter the keywordHM6 Phylo.
FIGURE 42-1
Amniotes
Mammals Reptiles Modern Birds
Dinosaursextinct
Archaeopteryxextinct
Caudipteryxextinct
archaeopteryx
from the Greek archaios,meaning “ancient,” and pteryx,
meaning “wing”
Word Roots and Origins
www.scilinks.orgTopic: BirdsKeyword: HM60168
842
• Gifted and TalentedStrategiesStrategiesINCLUSIONINCLUSION
Teaching TipSparse Fossil Record Ask stu-dents why bird fossils are rarerthan reptile or mammal fossils.(Sample answer: The hollow skeletonsof birds are less durable than reptile ormammal bones. Bird bones likely disinte-grated before fossilization occurred.)
Interpersonal
Birds Have students research thecharacteristics of birds by usingthe Internet Connect box on thispage. Intrapersonal
DiscussionSurviving a CatastropheAsk students what traits mayhave helped birds survive theCretaceous mass extinction. (Theycould fly far to find food and mates. Theirability to maintain a stable body temper-ature allowed them to survive climaticchanges.) Logical LS
GENERAL
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GENERAL
LS
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TEACHER RESOURCES
Technology
Transparencies• I24 Phylogenetic Diagram of
Birds, Reptiles, and Mammals
Students who are gifted and talented bene-fit from opportunities to learn beyond theconfines of the classroom and to expandtheir classroom learning to the worldaround them. They also use their talentsmore fully when they are asked to organizedetails and to make comparisons and judgments.
Ask students to research and prepare areport on the events surrounding the dis-covery of the first Archaeopteryx fossil in1861. Tell students that this reptile-bird“missing link” was discovered soon afterDarwin published his theory of evolution,and ask them to evaluate how the discov-ery related to Darwin’s theory.
Interpreting Visuals Havestudents examine the fossil ofArchaeopteryx lithographica inFigure 42-2. Ask students whythey think it was important thatthe fossil formed in lithographicsandstone. (Sandstone is fine-grainedand allowed the imprint of the feathersto be preserved and easily visible.)
Visual
ReteachingCharacteristic Review Withoutusing the text, have studentswrite down as many of the 7 important bird characteristicsas they can remember. Then,have them review the section tosee how accurate they were andto review any characteristics thatthey could not remember. Whenstudents have finished, havethem write down two avian andtwo reptilian characteristics ofArchaeopteryx. (avian: feathers,hollow bones; reptilian: teeth, longbony tail) Logical
QuizTrue or False: 1.The best characteristic for
identifying a bird is the presence of wings. (false, otheranimals also have wings but onlybirds have feathers)
2.The name Archaeopteryxcomes from Greek, meaning“ancient wing.” (true)
3.Archaeopteryx had both birdand reptile characteristics.(true)
4.Biologists are now certainabout how flight in birds originated. (false, there are twocompeting hypotheses about howflight originated)
GENERAL
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B I R D S 843
1. List two unique features of a bird’s skeleton.
2. What are two functions of feathers?
3. Identify the characteristics that birds have incommon with dinosaurs.
4. Describe two characteristics shared byArchaeopteryx and modern birds.
5. Name two differences between Archaeopteryxand modern birds.
6. Summarize the two major hypotheses for theevolution of flight.
CRITICAL THINKING
7. Forming Hypotheses Modern birds lack teeth.Form a hypothesis to explain how birds mighthave evolved to lack teeth.
8. Evaluating Hypotheses After studying the fos-sil of Archaeopteryx, evaluate the two hypothe-ses for the evolution of flight. Identify strengthsand weaknesses of each.
9. Applying Information Identify three adapta-tions that help birds satisfy their high need foroxygen.
SECTION 1 REVIEW
(b) Archaeopteryx
(c) Ichthyornis
(d) Hesperornis
In this fossil of Archaeopteryx (a), onecan find characteristics of both birdsand dinosaurs. These artist’s renderingsof three extinct birds are based on fossilevidence. Archaeopteryx (b) is the oldestbird; it still had claws on its wings.Ichthyornis (c) had strongly developedwings and was about 21–26 cm (8–10 in.) in length. Hesperornis (d)was considered flightless, but its well-developed legs made it a strong swimmer.
FIGURE 42-2
Another hypothesis draws on the fact that the dinosaurs mostclosely related to birds were terrestrial and states that the evolu-tion of birds must have occurred on the ground, not in the trees.Wings may have originally served to stabilize the animals as theyleapt after prey. Or they may have been used for trapping or knock-ing down insect prey. Over generations, the wings became largeenough to allow the animal to become airborne.
Evolution After ArchaeopteryxA number of recent discoveries show that by the early Cretaceousperiod (146–66 million years ago), birds had begun diversifying.Sinornis, a 140-million-year-old specimen discovered in China in1987, had some key features of modern birds, including a short-ened, fused tail and a wrist joint that allowed the wings to be foldedagainst the body. The diversification of birds continued throughoutthe Cretaceous period. Figures 42-2c and 42-2d show two birdsfrom the late Cretaceous period.
Only two of the modern orders of birds had appeared by the endof the Cretaceous period. Birds survived the global catastrophethat is thought to have wiped out the dinosaurs, and then under-went a dramatic and rapid evolutionary radiation. By about 40 mil-lion years ago, most of the modern orders of birds had originated.
(a)
843
Answers to Section Review
1. The skeleton has lightweight, hollow bones, someof which are penetrated by air sacs. Some of thebones are fused to make the skeleton rigid.
2. Feathers aid in flight and provide insulation.3. Birds and dinosaurs share a flexible, S-shaped
neck, a unique ankle joint, and hollow bones.4. Modern birds and Archaeopteryx share feathers,
wings, hollow bones, and a furcula.5. Unlike modern birds, Archaeopteryx had teeth,
claws on its forelimbs, and a long, bony tail.6. Hypothesis #1: Tree-dwelling dinosaurs first
evolved the ability to glide. Then, they developedthe ability to fly. Hypothesis #2: Flight evolvedamong ground-dwelling dinosaurs that used wingsas stabilizers or to capture prey.
7. Answers may vary. Sample answer: Teeth werelost because they were heavy.
8. Sample answer: The hypotheses that flight evolvedin tree-dwelling reptiles is supported by the factthat Archaeopteryx and had claws which would begood for climbing. The hypothesis that flight evolvedin land-dwelling reptiles is supported by the factthat Archaeopteryx has long legs, like the terrestrialreptiles most closely related to them.
9. Sample answer: A system of air sacs connected tothe lungs ensures constant air flow through thelungs. A very rapid metabolic rate helps oxygenmove through the bloodstream rapidly. A lightweightskeleton helps the bird conserve energy and oxygenfor flight muscles.
OverviewBefore beginning this section,review with students the Objectives listed in the StudentEdition. This section describesfeathers and the avian skeleton. It also discusses adaptations inbirds’ respiratory and digestivesystems. Reproductive and devel-opment strategies are discussed.Students will also learn aboutbirds’ migration.
Wear a down-filled jacket to class.Discuss the fact that bird down isone of the best heat insulatorsknown. Explain how down featherstrap a layer of warm air aroundthe bird’s body. Auditory
ActivityLift Give students two sheets ofpaper each. Have students punchabout 30 holes in one of the sheetsof paper. Using tape, drinkingstraws and string, have studentsmake kites out of each piece ofpaper. Then take the class outsideto test their kites. Ask studentsto notice which piece of papermade the better kite. (Students’observations may vary, but in generalthe paper without holes should make abetter kite.) KinestheticLS
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Focus
844 C H A P T E R 4 2
Bird feathers, such as this contourfeather (a), usually have a shaft, withtwo vanes growing out either side ofthe shaft. The vanes (b) consist of barbsand barbules that interlock by means of hooks.
FIGURE 42-3
C H A R A C T E R I S T I C S
O F B I R D SA number of unique anatomical, physiological, and behavioral
adaptations enable birds to meet the aerodynamic requirements
of flight. Natural selection has favored a lightweight body and
powerful wing muscles that give birds their strength.
FEATHERSFeathers are modified scales that serve two primary functions:providing lift for flight and conserving body heat. Soft, fluffy downfeathers cover the body of very young birds and provide an insu-lating undercoat in adults. Contour feathers give adult birds theirstreamlined shape and provide coloration and additional insula-tion. Flight feathers are specialized contour feathers on the wingsand tail. Birds also have dust-filtering bristles near their nostrils.
The structure of a feather combines maximum strength withminimum weight. Feathers develop from tiny pits in the skin calledfollicles. A shaft emerges from the follicle, and two vanes, picturedin Figure 42-3a, develop on opposite sides of the shaft. At maturity,each vane has many branches, called barbs. The barbs, in turn,have many projections, called barbules, equipped with micro-scopic hooks, as shown in Figure 42-3b. The hooks interlock andgive the feather its sturdy but flexible shape. Feathers are made ofkeratin, an insoluble protein that is highly resistant to decomposi-tion. Keratin is also the protein that makes up fingernails, claws,hair, and scales in animals.
Feathers need care. In a process called preening, birds use theirbeaks to rub their feathers with oil secreted by a preen gland,located at the base of the tail. Birds periodically molt, or shed andregrow their feathers. Birds living in temperate climates usuallyreplace their flight feathers during the late summer.
SECTION 2
O B J E C T I V E S
● Describe the structure of a contourfeather.
● Identify two modifications forflight seen in a bird’s skeletalsystem.
● Contrast the function of thegizzard with that of the crop.
● Trace the movement of air throughthe respiratory system of a bird.
● Explain the differences betweenaltricial and precocial young.
V O C A B U L A R Y
featherfollicleshaftvanebarbbarbulepreen glandsternumpygostylecropproventriculusgizzardvas deferensoviductbrood patchprecocialaltricialornithologist
BarbShaft Barbule
Vane
Hooks(a) (b)
844
SECTION 2
Death by Oil Birds that get caught in oil spillsoften die of hypothermia (lowered body temperature). Ask students to explain howan oil-soaked bird becomes hypothermic.(When the feathers become soaked with oil, the feath-ers can no longer effectively insulate the bird’s body.)
TEACHER RESOURCES
Workbooks
Active Reading Guide (Section 2)
Quick, Data, and Math Labs• Calculating Average Bone Density
Technology
Transparencies• I25 External Structure of Birds—Bald Eagle• I26 Internal Structure of Birds—Bald Eagle• I27 Contour Feather Structure
Visual Concepts CD-ROM• Bird Adaptations for Flight, Parts of a Feather,
Preening
GENERAL
ActivityBone Density Give students acow bone (can be obtained froma local butcher shop) and a chickenbone. Write the formula for density(d �mass/volume) on the board.Have students use graduatedcylinders to determine the bones’volume by displacement. Theyshould use a balance to determinethe mass of the bones. Have stu-dents calculate the density ofeach bone and determine whichbone has the higher density. (Thecow bone should have a higher density.)Discuss the adaptive value of hol-low bones for birds. (Sample answer:Hollow bones are lighter, which allowsfor flight.) Kinesthetic
Comparing Wing StructuresTime Required 20 minutes
Procedural Tips Obtain severalimages of eagles, penguins, falcons,and owls. Use the images to makea sheet for each type of bird. Copythe pages for students or hangthe pages up where students cantake turns examining the images.
Answers to Analysis Answers will varydepending on which birds are shown.Sample answers: Some eagles live highin trees. They have wide wingspans forsoaring in open spaces. Their hugewingspan would hinder them in a lessopen environment. Penguins live in anaquatic environment. Their short wingsare adapted to be used for swimming.Penguin wings are not useful for escap-ing predators on land. Owls and falconswings have a short to medium wing spanand are well suited for maneuverability.Owls have “silent feathering” for quietflight. Owls might not be competitivewhere there are birds that are betteradapted to the environment and othertypes of resources available.
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B I R D S 845
SKELETON AND MUSCLESThe avian skeleton combines lightness with strength. The bonesare thin and hollow. Many bones are fused, so the skeleton is morerigid than the skeleton of a reptile or mammal. The rigid skeletonprovides stability during flight. Note in Figure 42-4 that the bonesof the trunk and hip vertebrae and the pectoral and pelvic girdlesare highly fused. Along with the furcula, the large, keel-shapedsternum, or breastbone, is an attachment point for flight muscles.The humerus, ulna, and radius, along with the pectoral girdle andthe sternum, support the wing. The pygostyle (PIEG-uh-stiel), thefused terminal vertebrae of the spine, supports the tail feathers.The tail provides additional lift and aids in steering and braking.
Flight involves a series of complex wing movements, each oneusing a different set of muscles. On the downstroke, the wings cutforward and downward through the air. During upstroke, they moveupward and backward. These movements are made possible bylarge, powerful flight muscles in the breast and wings. In some birds,flight muscles account for up to 50 percent of the body weight.
METABOLISM Birds are endothermic; that is, they generate heat to warm the bodyinternally. Rapid breathing and digestion of large quantities of foodsupport the high metabolic rate necessary to generate this heat.Birds, unlike reptiles, cannot go for long periods without eating. Tohelp conserve body heat, birds may fluff out their feathers. Aquaticbirds have a thin layer of fat that provides additional insulation.
Ulna
Radius
Humerus
Cranium
Maxilla
Mandible
Pectoralgirdle Scapula
Furcula
Coracoid Rib
Sternum
Femur
Pelvic girdle(fused ischium, ilium, and pubis)
Fibula
Pygostyle
Tarsometatarsus
Tibiotarsus
The avian skeleton is well adapted forflight. The bones are air filled, makingthem light but strong. The skeleton isarranged in such a way that it supportsthe large muscles necessary for flight.
FIGURE 42-4
Comparing WingStructures
Materials pictures of differentkinds of birds, ruler
Procedure Examine each sheet ofbirds and their wings. Compare thestructure and shape of the wings.Measure the wingspan relative tothe bird’s body length. Record yourobservations.
Analysis Predict the type of habi-tat in which each bird lives. Howdoes the shape of the wing relate tothe bird’s niche? Explain why thetype of wings each bird has mightmake the bird unsuccessful if itwere introduced into a much differ-ent environment.
Quick Lab
845
Cultural Symbols Birds have beenimportant cultural symbols throughoutthe world. Eagles, for example, havebeen adopted as national symbols in the United States, Russia, Mexico, andGermany. The vulture was an importanticon in ancient Egypt, and the mythicalphoenix of ancient Greece was also animportant symbol.
CulturalAwarenessCulturalAwareness
TEACHER RESOURCES
Workbooks
Datasheets for In-Text Labs• Comparing Wing Structures
Technology
Transparencies• I28 Avian Skeleton
Visual Concepts CD-ROM• Anatomy of a Bird, Bird Digestive System
GENERAL
Using the FigureBird Stomach Draw students’attention to Figure 42-5 andpoint out that the bird stomach is divided into two parts: theproventriculus and the gizzard.Ask students why the phrase“scarce as hen’s teeth” can beexplained by the structure andfunction of the bird stomach.(Birds do not have teeth. Instead, thegizzard often contains stones to helpgrind food. It serves the same functionas teeth.) Visual
Teaching TipSeed Dispersal Fruit-eating birdsare instrumental in distributingthe seeds of many kinds of plants.Explain to students that the rapiddigestive system of birds oftendigests only the seed coat, excret-ing a seed ready to germinate,complete with fertilizer (feces). In the western United States, manybirds relish the fruit of poisonoak. Fence rows are often linedwith this rash-causing plantbecause birds sit on the fenceand distribute the seeds.
Auditory
Teaching TipBird Digestion Have studentsmake a Graphic Organizer similarto the one at the bottom of thispage to show the sequence ofstructures in the avian digestivesystem. VisualLS
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846 C H A P T E R 4 2
Digestive and Excretory SystemsThe high amount of energy required to fly and regulate body heatis obtained by a quick and efficient digestive system, as illustratedin Figure 42-5. Because birds do not have teeth, they are not ableto chew their food. Instead, food passes from the mouth cavitystraight to the esophagus. An enlargement of the esophagus calledthe crop stores and moistens food. Food then passes to the two-part stomach. In the first chamber, the proventriculus(PROH-ven-TRIK-yoo-luhs), acid and digestive enzymes begin breakingdown the food. Food then passes to the gizzard, the muscular por-tion of the stomach, which kneads and crushes the food. The giz-zard often contains small stones that the bird has swallowed.These aid in the grinding process. Thus, the gizzard performs afunction similar to that of teeth and jaws. Seed-eating birds usuallyhave a larger crop and gizzard—relative to body size—than meat-eating birds do.
From the stomach, food passes into the small intestine. There,bile from the liver and enzymes from the pancreas and intestinefurther break down the food. The nutrients are then absorbed intothe bird’s bloodstream. Passage of food through the digestive sys-tem of a bird is usually very rapid. For instance, a thrush can eatblackberries, digest them, and excrete the seeds 45 minutes later.
The avian excretory system is efficient and lightweight. Unlikeother vertebrates, most birds do not store liquid waste in a urinarybladder. The two kidneys filter a nitrogenous waste called uric acidfrom the blood. Concentrated uric acid travels through ductscalled ureters to the cloaca, where it mixes with feces and is thenexcreted. This system is adaptive for flight because birds do notneed to carry much water in their bodies.
proventriculus
from the Greek pro, meaning“before,” and the Latin venter,
meaning “belly”
Word Roots and Origins
Esophagus
Proventriculus
Gizzard
Kidney
Large intestineCrop
Heart
Liver
Pancreas
Small intestine
Cloaca
A bird’s digestive and excretory systemsare adapted for the rapid processing offood and metabolic wastes. The highenergy requirements of flight make thisefficient system necessary. For example,the carnivorous shrike can digest amouse in three hours.
FIGURE 42-5
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Use this Graphic Organizer with Teaching Tip:Bird Digestion on this page.
Mouth Esophagus ProventriculusCrop
GizzardSmall IntestineLarge Intestine
Cloaca
Teaching TipAvian Diagnosis Tell studentsthat a boy took his sick pet birdto a veterinarian. The boy toldthe vet that the bird would not flywhen he took it out of its cage.After examining the bird, the vettold the boy that the bird has asevere respiratory infection. Askstudents how this diagnosisexplains the bird’s inability to fly.(If its respiratory system is not functioningcorrectly, the bird cannot get sufficientoxygen to power its flight.) Logical
ActivityBird Heart Model Divide the class into groups. Give each groupa shoe box (with cover), an 11 in. � 17 in. sheet of posterboard, a blue and red marker, fourwhite straws, tape, and scissors.Supply a diagram that shows theexternal and internal structure ofa bird’s heart. Have students builda model of a bird’s heart. The shoebox represents the outside of the heart. The poster board andstraws should be used to make thechambers and the four main bloodvessels of the heart. Studentsshould use markers to color-codethe blood vessels—red for oxy-genated blood and blue for deoxy-genated blood. Students shouldattach a sheet of paper explainingthe function of the avian heart.
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Active Reading After studentshave read this section silently,have pairs of students summarizeto each other what they have readwithout looking at the textbook.Students should listen to theirpartners without interrupting.Then, they should point out anyinaccuracies in the summary andadd any ideas that were left out.Students may refer to the textbookduring this clarification process.
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Respiratory System The high metabolic rate of birds requires large amounts of oxygen.Yet some birds migrate thousands of miles at altitudes as high as7,000 m (23,000 ft), where air pressure is very low. So, birds havean elaborate and highly efficient respiratory system. Air enters thebird’s body through paired nostrils located near the base of thebeak. The air passes down the trachea and enters the two primarybronchi. From the bronchi, some of the air moves to the lungs.However, about 75 percent of the air bypasses the lungs and flowsdirectly to posterior air sacs, shown in Figure 42-6. In most birds,nine sacs extend from the lungs and occupy a large portion of thebird’s chest and abdominal cavity. These sacs also extend intosome of the long bones. Thus, the air sacs not only function in res-piration but also greatly reduce the bird’s density.
Gas exchange does not occur in the air sacs. Their function is tostore and redirect air. When the bird exhales, the oxygen-poor airfrom its lungs is forced into the anterior air sacs, and the oxygen-richair in the posterior air sacs is forced into the lungs. This way, the birdhas oxygenated air in its lungs during both inhalation and exhalation.
Circulatory SystemThe avian circulatory system has characteristics that are similar tothose of either reptiles or mammals or both. Like crocodiles andmammals, birds have a four-chambered heart with two separateventricles. Deoxygenated blood is always kept separate from oxy-genated blood. In comparison with most other vertebrates, mostbirds have a rapid heartbeat. A hummingbird’s heart beats about600 times a minute. An active chickadee’s heart beats 1,000 timesa minute. In contrast, the heart of the larger, less active ostrichaverages 70 beats per minute, or about the same rate as a humanheart. Avian red blood cells have nuclei.
Lung
Trachea
Anteriorair sacs
Posteriorair sacs
The unique architecture of the bird’srespiratory system provides a constantflow of oxygenated air to the lungs. Thishighly efficient system allows birds tomaintain the high metabolic ratenecessary for flight. It also enables birdsto function at high altitudes, whereother animals would suffer from the lowavailability of oxygen.
FIGURE 42-6
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Birding Birding, or birdwatching has beendescribed as the second-favorite outdooractivity, after gardening, in the United States.Invite a local naturalist to visit your class-room and discuss how to attract and identify backyard birds. Make a list of local birds and show slides of each bird to your class.
TEACHER RESOURCES
Technology
Transparencies• I29 Avian Heart Structure• I30 Avian Lung Structure
Visual Concepts CD-ROM• Bird Lungs, Bird Heart, Parts of a Bird Brain
Group ActivityBird Songs Tell students thatmany bird species sing to attractmates or to establish territories.Obtain a recording of bird songs.Have groups of three or four stu-dents learn to identify a birdsong. Provide them with birdidentification books to researchthe bird that produces the song.Have each group imitate the songand report about their bird to therest of the class. Play the birdsong recording of each group’sparticular bird after they finishtheir presentation to see howclosely their imitation soundedlike the recorded song.
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Nervous System and Sense OrgansRelative to their body size, birds have large brains. The most highlydeveloped areas of the bird’s brain are those that control flight-related functions, such as the cerebellum, which coordinates move-ment. The cerebrum is also large. It controls complex behaviorpatterns, such as navigation, mating, nest building, and caring forthe young. The large optic lobes receive and interpret visual stimuli.
Keen vision is necessary for taking off, landing, spotting land-marks, hunting, and feeding. Most birds have strong, color visionthat aids them in finding food. In most species, the eyes are largeand are located near the sides of the head, giving the bird a widefield of vision. Birds that have eyes located near the front of thehead have better binocular vision, meaning they can perceivedepth in the area where the visual fields of the two eyes overlap.
Hearing is important to songbirds and to nocturnal species,such as owls, which rely on sounds to help them locate their prey.Though birds lack external ears, owls have feathers around theirear openings that direct sound into the ear. The sense of smell isalso strong in many birds.
REPRODUCTIONIn the male bird, sperm is produced in two testes that lie anteriorto the kidneys. Sperm passes through small tubes called vasadeferentia (singular, vas deferens) into the male’s cloaca. Duringmating, the male presses his cloaca to the female’s cloaca andreleases sperm. Most females have a single ovary located on theleft side of the body. The ovary releases eggs into a long funnel-shaped oviduct, where the eggs are fertilized by sperm. Fertilizedeggs move down the oviduct, where they are encased in a protec-tive covering and a shell. The egg passes out of the oviduct andinto the cloaca. From the cloaca, it is expelled from the bird.
Nest Building and Parental CareBirds usually lay their eggs in a nest. Nests hold the eggs, concealyoung birds from predators, provide shelter from the elements,and sometimes serve to attract a mate. Most birds build nests insheltered, well-hidden spots—ranging from holes in the ground totreetops. Woodpeckers, for example, nest in a hole they havedrilled in a tree. Orioles suspend their nests from branches, wellbeyond the reach of predators. And barn swallows build a saucerof mud on the beam of a building. Birds construct their nests fromalmost any available material. Twigs, bark, grasses, feathers, andmud are common materials used.
One or both parents warm, or incubate, the eggs by sitting onthem and covering them with a thickened, featherless patch of skinon the abdomen called a brood patch. Once the eggs hatch, theyoung usually receive extensive parental care.
ConnectionConnectionEcoEcoDDT and Bird EggsDDT is a pesticide that was widelyused on crops until the 1970s. DDTwas banned in several countriesbecause of the harm it was causingto birds. DDT causes some birds toproduce thin egg shells, decreasingsurvival rates of the birds’ off-spring. The result was a significantdrop in the populations of severalspecies of raptors and pelicans. Thethinning of the eggs was so signifi-cant that even the weight of anincubating parent could crush theeggs. With the banning of DDT inthe United States, populations ofthe affected birds have increased.
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ConnectionConnectionEcoEcoHave students research specificbird species that were significantlyaffected by DDT. Have them useapproved online resources to findthe species numbers before andafter the DDT ban in 1972. Baldeagles and ospreys would begood birds to research, alongwith pelicans. Students shouldreport their findings to the class.
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Uses of Feathers Have students uselibrary and online resources to researchthe uses and significance of feathers inindigenous cultures. Students could exam-ine the use of feathers in clothing and art,their ceremonial significance, their use asindicators of status within the tribe, or thesignificance of the species of birds fromwhich feathers are obtained. Suggest thatstudents study Native American tribes orpre-Columbian civilizations. Have studentspresent oral reports based on their findings.
Brood Parasites The brown-headed cowbirdis a brood parasite. A female cowbird will flyto a nest full of eggs, roll an egg or two out,and lay an egg or two to replace the missingeggs. When the nest’s owner returns, it willincubate all the eggs, including the cowbird’seggs. The cowbird eggs often have a shorterincubation time and will hatch first. The cowbird nestlings are then fed first and get a head start in their development over theother birds in the nest. Cowbird nestlings mayeven eject the other nestlings, eliminatingcompetition for food.
Science Literacy Have studentsresearch a migratory bird speciesfrom the Northern Hemisphere,such as songbirds, waterfowl, and birds of prey. Have other stu-dents research a migrant from the Southern Hemisphere (mostlynon-singing birds, such as cuckoos,nightjars, and swifts). Have themreport on their bird’s adaptationsand natural history. Reports shouldinclude where the bird summersand winters as well as informa-tion on its breeding and nestingbehaviors. Verbal
Vocabulary Have students makenote cards to study the vocabu-lary in this section. Have studentswrite a term on one side of thecard and its meaning on the other.Encourage English languagelearners to write the vocabularyand definitions both in Englishand in their native language. Verbal
ReteachingBird Characteristics On theboard, have students create atable describing the characteristicsof avian feathers and the aviandigestive, respiratory, circulatory,and nervous systems. Then, askstudents to identify how each isadapted to help the bird survive.
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QuizTrue or False:1. If a person finds a living animal
that has feathers, it is a bird.(true)
2.Natural selection has favored alightweight body in birds. (true)
3. Most birds have a relativelylow metabolic rate. (false, allbirds have a high metabolic rate)
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Birds have two general patterns of rearing young. Some birds laymany eggs and incubate them for long periods. These birds hatchprecocial (pree-KOH-shuhl) young, which can walk, swim, and feedthemselves as soon as they hatch. Ducks, quail, chickens, andother ground-nesting species produce precocial offspring. Otherbirds lay only a few eggs that hatch quickly and produce altricial(al-TRISH-uhl) young, which are blind, naked, and helpless, as shownin Figure 42-7. These young depend on both parents for severalweeks. The young of woodpeckers, hawks, pigeons, parrots, war-blers, and many aquatic birds are altricial.
MIGRATION Each year, thousands of bird species exploit the spring and sum-mer food resources of temperate regions. Then, when tempera-tures drop and the food supply dwindles, they travel to warmerclimates. The seasonal movement of animals from one habitat toanother habitat is called migration. Many of the birds that nest inthe United States and Canada during the spring and summer flysouth in the fall to spend the winter in Mexico, Central America,the Caribbean, or South America.
How do birds manage to navigate thousands of kilometersacross varied terrains and return to the same places each year?Ornithologists—biologists who study birds—have learned thatbirds rely on a variety of cues to help them navigate. Some speciesmonitor the position of the stars or the sun. Others rely on topo-graphical landmarks, such as mountains. The Earth’s magneticfield, changes in air pressure due to altitude, and low-frequencysounds may also provide information to migrating birds.
Many species migrate thousands of kilometers and must rely ontheir fat reserves in order to complete the journey. To prepare fortheir migration, some birds, such as blackpoll warblers, eat somuch food before their journey that their weight nearly doubles.
1. Distinguish between vanes, barbs, and barbules.
2. What is the function of the keel-shaped sternum?
3. In what way does the gizzard compensate forthe lack of teeth in birds?
4. What are the functions of the anterior andposterior air sacs?
5. Contrast altricial and precocial young.
6. Identify the cues birds use to help themnavigate during a migration.
CRITICAL THINKING
7. Analyzing Information Why do you think thebrood patch is featherless?
8. Applying Information Ground-nesting birdsoften produce precocial young. How might thisimprove the odds of survival for the young?
9. Forming Reasoned Opinions Some biologistshave proposed that birds and reptiles should begrouped in the same class of vertebrates. Do youagree? Support your answer.
SECTION 2 REVIEW
This yellow warbler cares for its youngby feeding and protecting them.
FIGURE 42-7
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Answers to Section Review
1. The two vanes grow out on either side of the shaft.Barbs are the parallel branches that make up thevanes. Barbules are projections on the barbs thatinterlock with one another.
2. Major flight muscles anchor to the keel.3. The gizzard, which often contains small stones,
kneads and crushes food.4. The air sacs store air but do not participate in gas
exchange. The posterior air sacs hold oxygen-richair and send it to the lungs. The anterior air sacshold oxygen-depleted air from the lungs.
5. Precocial young can walk, swim, and feed as soonas they hatch. They hatch from large broods andare incubated for a long time. Altricial young hatch
from small broods after a short incubation period.When they hatch their eyes are still sealed andthey are featherless.
6. the position of the stars and sun, landmarks, possiblyby magnetic fields, changes in air pressure, andlow-frequency sounds
7. Sample answer: Feathers would prevent thetransfer of heat to the incubating eggs.
8. Sample answer: Ground-dwelling birds’ nests arevulnerable to predators. Precocial birds can followtheir mother, who can then protect them.
9. Answers may vary but should be supported byscientific evidence, such as the characteristicsshared by both groups or the differences betweenthe groups.
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S C I E N C ET E C H N O L O G YS O C I E T Y
Delaware Bay, located between Delaware and New Jersey, is a staging sitefor shorebirds that migrate between South America and the Arctic. Asmuch as 80 percent of the population of red knots (shown here) feeds andrests at this site.
MIGRATING BIRDS IN DANGER:Conservation Issues and Strategies
Since Europeans first set-tled in the Americas,more than half of the
Western hemisphere’s wetlandshave been destroyed. Today, inspite of regulations, wetlanddestruction continues.
Crucial Roadside Park
More than 40 North Americanshorebird species—such assandpipers, plovers, andcurlews—breed in the Arcticand migrate to wintering sitesin Central and South America.To complete these long-distance flights, shorebirdsmust accumulate large fuelreserves. The birds prepare fortheir journeys at a few food-rich staging areas, which areusually wetlands. In somecases, between 50 and 80 per-cent of the entire population ofa species may visit a singlesite. The loss of such a stagingarea could devastate a popula-tion of shorebirds.
Studies show that the num-bers of shorebirds are decliningworldwide. In order to preserveand protect these valuablespecies, researchers must firstdetermine shorebird populationsand map their migratory routes.
Technology to the Rescue
Today, the work of preservingshorebirds has been greatlyadvanced through the use ofcomputer technology. One groupthat uses computers in this workis the International ShorebirdSurvey (ISS). The ISS was estab-lished in 1974 and consists ofboth volunteers and professionalresearchers. The volunteersrecord information on popula-tions, habitat characteristics,weather conditions, and humanactivity. Researchers use com-puter programs to identify rela-tionships among these variables.Complex methods of analysishave revealed much about themigratory habits of shorebirds—
their velocity, altitude, flight path,and gathering sites, for example.Computer analyses have alsohelped researchers identify sig-nificant trends, such as a 70 to 80percent drop in the population ofsanderlings.
Sanctuary Without Borders
Another organization that worksto protect shorebirds is theWestern Hemisphere ShorebirdReserve Network (WHSRN). TheWHSRN has identified morethan 90 sites where significantnumbers of shorebirds breed,feed, and rest. The organizationhas proposed that these sites berecognized internationally as asingle, vast wildlife reservewhose boundaries are, in effect,defined by the migrating birds.
Because most of the stagingsites for shorebirds are wet-lands, humans must develop astrategy for the conservation ofthese sites. The hemisphericwildlife reserve is one exampleof such a strategy.
1. What are some threats toshorebirds posed by humans?
2. How is technology aiding theconservation of shorebirds?
3. Critical Thinking How do themigration behaviors of shore-birds make them especiallyvulnerable to habitat loss?
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www.scilinks.orgTopic: Migration of BirdsKeyword: HM60963
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BackgroundIn the United States, the U.S. Fish andWildlife Service is one of many govern-ment organizations that work to protectmigratory bird habitats. One way by whichthe U.S. Fish and Wildlife Service raisesmoney to protect migratory bird habitat is by the sale of Federal Migratory BirdHunting and Conservation Stamps, or"duck stamps." Migratory waterfowlhunters over the age of 16 are required topurchase duck stamps, and birders canpurchase duck stamps to gain free admis-sion to national bird refuges. Collectors,conservationists, and educators also pur-chase the stamps. The money raised bythe sale of these stamps is used to estab-lish wetland refuges for migratory water-fowl. These wetlands become part of theNational Wildlife Refuge System. Since1934, the sale of duck stamps has gener-ated enough revenue to purchase or leasemore than 5 million acres of migratorywaterfowl habitat in the United States.
DiscussionGuide the discussion by posing the following questions.
1. What are researchers’ first tasks intrying to preserve shorebirds?(Researchers must first determineshorebird populations and map theirmigratory routes.)
2. What are the names of two groupsmentioned in this feature that usecomputers, and what do they do? (The International Shorebird Surveyidentifies relationships among shore-bird populations, habitat characteris-tics, weather conditions, and humanactivity. The Western HemisphereShorebird Reserve Network identifieswhere shorebirds breed, rest, and feed.) 3. Why are shorebirds vulnerable to human activity?
(Shorebirds are vulnerable because they congre-gate in a few strategic sites.)
Review Answers
1. Answers may vary. Students should note that anyhuman activity that impacts key wetland stagingareas can adversely affect the shorebird population.
2. By collecting and entering information aboutshorebirds into computer models, scientists arelearning important information about migration patterns, populations, and staging sites.
3. When migrating, many shorebirds congregate at afew large wetland staging areas. In some cases, asmuch as 80% of a particular population may visit asingle site. This makes the population extremelyvulnerable to changes in or loss of wetland staging areas.
OverviewBefore beginning this section,review with students the Objectives listed in the StudentEdition. This section describeshow different types of birds havebeaks and feet adapted to exploittheir particular habitat. Ten ordersof living birds are summarized.
Ask students to contribute thecommon names of as many birdsas possible in 5 minutes. Writeeach name on the board as it isoffered. When time is up, ask stu-dents to suggest which birds onthe list are closely related to eachother. Logical
DemonstrationBird Feet Bring in a chicken foot.(They can often be purchased insupermarkets.) Ask students ifthe foot would be well-adaptedfor life in water. (no) Ask if itappears well-adapted for captur-ing prey. (no) Ask students todescribe its probable function. (It is used for scratching the ground for seeds.) Visual
Classification of Birds Have stu-dents research bird taxonomy byusing the Internet Connect boxon this page. Intrapersonal
Reading Organizer Instead ofhaving students try to memorizethe names of bird orders and alltheir characteristics as they read,encourage students to write out alist of key characteristics of thebirds in each order. This will helpthem understand how birds areclassified into different orders.
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C L A S S I F I C A T I O NBirds are the most widespread terrestrial vertebrates. Their
ability to navigate over long distances and their many
adaptations for flight enable them to migrate to and inhabit
virtually any environment. Their anatomical diversity reflects
the diversity of places they inhabit.
DIVERSITYBy looking closely at a bird’s beak and feet, you can infer manythings about where it lives and how it feeds. Hawks and eagleshave powerful beaks and clawed talons that help them capture andtear apart their prey. Swifts have a tiny beak that opens wide like acatcher’s mitt and snares insects in midair. Because swifts spendmost of their lives in flight, their feet are small and adapted forinfrequent perching. The feet of flightless birds, on the other hand,are modified for walking and running. Some examples of the vari-ety of bird beaks and feet are shown in Figure 42-8.
SECTION 3
O B J E C T I V E S● Describe the relationship between
beak shape and diet in birds.● List 10 major orders of living birds,
and name an example of eachorder.
● Describe the function of the syrinx.
V O C A B U L A R Ysyrinxcrop milk
(a) (b)
(c) (d)
This cardinal (a), Cardinalis cardinalis,has a short, strong beak for crackingseeds and feet that enable it to perchon small tree branches. This kestrel(b), Falco sparverius, has a beak thatenables it to tear flesh and talons thatenable it to grip and kill prey. Thiscalliope hummingbird (c), Stellulacalliope, has a long, thin beak thatenables it to extract nectar fromflowers. This northern shoveler (d),Anas clypeata, has a flat beak thatenables it to shovel mud whilesearching for food.
FIGURE 42-8
www.scilinks.orgTopic: Classification of
BirdsKeyword: HM60297
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TEACHER RESOURCES
Workbooks
Active Reading Guide (Section 3)
Technology
Transparencies• I31 Avian Adaptations
Visual Concepts CD-ROM• Beak Adaptations and Bird Diversity, Foot
Adaptations and Bird Diversity, Types of Birds
Teaching TipOwl Pellets Tell students thatowls cough up pellets that con-tain the undigested bones of theirprey. Then, ask students whymammalogists collect owl pellets.(By analyzing the contents of the pellets,mammalogists can determine the kindsof small mammals that live in an area.)
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Science Literacy Introduce stu-dents to the various field guidesavailable for birders. Point outhow some field guides are organ-ized by bird color or body shape,but most field guides are organizedby bird orders. Have studentsexamine the field guides and notewhere various groups are foundin the book. (For example, waterfowlmay be found in the front, while song-birds may be found in the back of theguide.) Tell students that learningthe organization of a field guide isan important skill to have so thatthey can find a particular birdquickly. Visual
Teaching TipPreening with Feet Birds withlong bills have difficulty preeninghard-to-reach places, such as theback of the head and neck. Mostbirds solve the problem by usingtheir feet. Hummingbirds, forexample, spend almost half theirgrooming time using their feet.
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Most taxonomists divide about 10,000 species of living birdsinto 23 orders. Taxonomists have traditionally used morphologicalevidence from beaks, feet, plumage, bone structure, and muscula-ture to classify birds. Technological advances in the analysis ofblood proteins, chromosomes, and DNA have also been used morerecently. Despite the introduction of these new methods, the rela-tionships among the 23 orders of birds are still not well resolved.Ten of the most familiar orders of living birds are described below.
Order AnseriformesSwans, geese, and ducks—commonly called waterfowl—belong tothis order of 160 species. Found worldwide, members of this orderare usually aquatic and have webbed feet for paddling and swim-ming. Waterfowl feed on a variety of aquatic and terrestrial foods,ranging from small invertebrates and fish to grass. The bill is typi-cally flattened. The young are precocial, and parental care is usu-ally provided by the female. A mute swan is shown in Figure 42-9.
Order StrigiformesThis order includes the owls, the nocturnal counterparts to theraptors. Owls are predators that have a sharp, curved beak andsharp talons or claws. As shown in the chapter opener photo, owlsalso have large, forward-facing eyes that provide improved visionat night. Owls rely on their keen sense of hearing to help locateprey in the dark. There are about 180 species of owls, and they arefound throughout the world.
Order ApodiformesHummingbirds and swifts belong to this order. All of the roughly430 species are small, fast-flying, nimble birds with tiny feet. Swiftspursue insects and capture them in flight. Hummingbirds eat someinsects but also feed on nectar, which they lap up with a very longtongue. The long, narrow bill of a hummingbird can reach deep intoa flower to locate nectar. Swifts have a worldwide distribution, buthummingbirds live only in the Western Hemisphere.
Order PsittaciformesThis order includes the parrots and their relatives, the parakeets,macaws, cockatoos, and cockatiels. Most of the roughly 360 species in this order live in the tropics. Parrots are characterizedby a strong, hooked beak that is often used for opening seeds or slic-ing fruits. Their upper mandible is hinged on the skull and movable.Unlike most birds, parrots have two toes that point forward and twotoes that point toward the rear, an adaptation for perching andclimbing. They are vocal birds, and many species gather in large,noisy flocks. Parrots have long been prized as pets because of theircolorful plumage and intelligence and because some species can betaught to mimic human speech. However, habitat destruction andexcessive collecting for the pet trade now threaten many parrotspecies with extinction. Figure 42-10 shows a cockatoo.
The parrot pictured below is a lessersulfur-crested cockatoo, Cacatua
sulphurea. Parrots range in length from8 cm (3 in.) to over 91 cm (3 ft). Theearliest fossils of parrots indicate thatthey have existed as a group for at least20 million years. Like most parrots, thesecockatoos nest in holes in trees, andthey usually lay only two eggs per year.Because of human activities, manyspecies have become extinct orendangered.
FIGURE 42-10
This mute swan, Cygnus olor, is able to take off from water and fly at veryhigh speeds despite its great weight.Weighing up to 23 kg (50 lb), muteswans are the heaviest flying birds.Swans are monogamous, meaning theymate for life. While the female incubatesthe eggs, the male helps guard the nest.
FIGURE 42-9
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Students who have learning disabilities,developmental delays, or attention deficitdisorders are more likely to understandcomplex concepts if they are given a physi-cal representation that they can see or feel.Have students work in small groups.Assign each group an order of birds. Then,ask students to make a model of a bird
from that order. Students should make life-size models of their bird and label thecharacteristics of the bird that make it apart of the order in which it is classified.Encourage students to make a fact sheetabout the bird that describes the bird’shabitat, physical characteristics, and feeding habits.
Using the FigureAdaptive Advantage Have stu-dents examine the toucan inFigure 42-11 and speculate aboutwhat adaptive advantage its color-ing confers. (Biologists hypothesizethat the color scheme enables toucansto recognize members of their ownspecies.) Then, ask students whatadaptive advantage a large billprovides. (Biologists hypothesize thatthat the large bill frightens other birdsthat may represent a danger to potentialpredators, such as hawks.) Visual
ActivityObserving Wild Birds Take stu-dents to an area near the schoolto observe birds, such as a citypark, natural area, or refuge.Prepare them for birding by fur-nishing them with field guides ofbirds that live in your area. Havestudents create check-off lists forthe species they will most likelyencounter. Ask them to bringbinoculars from home if theyhave them, or supply one or two pairs for them to use.
Visual
ActivityBirdhouses One result of habitatdestruction is a reduction in nest-ing sites for birds. Have studentsaid wild birds by building housesfor them. Find free birdhouseplans on the Internet or in wood-worker magazines and obtaininexpensive wood from a localhome supply store. (You can alsouse recycled wood.) Ask yourwoodshop teacher or a localwoodworker to cut the wood forthe birdhouses. Supply hammersand nails, and have studentsassemble the birdhouses outsideso as not to disturb other classes.CAUTION: To protect their eyesand clothes, students shouldwear goggles and aprons.
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Order PiciformesThis diverse group of tree-dwelling birds contains woodpeckers,honeyguides, and toucans. All members of this order nest in treecavities. Like parrots, they have two forward-pointing toes and twothat point to the rear. There are about 350 species found through-out the world except in Australia. The diversity of foods consumedby these birds is reflected in the diversity of their bills.Woodpeckers, which drill holes into trees to capture insects, havestrong, sharp, chisel-like bills. Toucans feed mainly on fruit, whichthey pluck with a long bill, as shown in Figure 42-11.
Order PasseriformesThis large order contains about 5,900 species—more than half thetotal number of bird species—and includes most of the familiarNorth American birds. Robins, warblers, blue jays, and wrens arejust some of the birds belonging to this group.
Passerines are sometimes called perching birds. In most birds,three toes point forward and one points backward. Passerines, too,have this arrangement of toes, but the rear toe is enlarged and par-ticularly flexible to provide a better grip on branches. Passerinesfeed on a variety of foods, including nectar, seeds, fruit, and insects.
Many passerines are called songbirds because the males pro-duce long, elaborate, and melodious songs. Male birds sing to warnaway other males and to attract females. The song is produced inthe structure known as the syrinx (SIR-ingks), which is located at thebase of the bird’s trachea. By regulating the flow of air through thesyrinx, birds can generate songs of great range and complexity.
Order ColumbiformesThis globally distributed group contains about 320 species of pigeonsand doves. Figure 42-12 shows a mourning dove. These birds usuallyare plump-breasted and have relatively small heads; short necks,legs, and beaks; and short, slender bills. Most feed on fruit or grain.
The crop, which in most other birds is used to store food,secretes a nutritious milklike fluid called crop milk. Both sexesproduce crop milk to feed their young. Columbiform birds usuallylay a clutch of two eggs, which hatch after a two-week incubationperiod. The young usually leave the nest two weeks after hatching.Another member of this order is the now-extinct dodo of Mauritius,an island in the Indian Ocean.
Order CiconiiformesThe order Ciconiiformes is highly diverse, and has a worldwide dis-tribution. This order includes about 1040 species of herons, storks,ibises, egrets, raptors, and penguins. Many have a long, flexibleneck, long legs, and a long bill. Many are wading birds, and theyfeed on fish, frogs, and other small prey in shallow water. Manyspecies of Ciconiiformes are diurnal (daytime) hunters with keenvision. Vultures, however, feed on dead animals and use their senseof smell to detect the odor of decomposing flesh.
Toucans, such as this keel-billed toucan,Ramphastos sulfuratus, mate once peryear, usually laying two to four eggs. Themale and female toucans take turnssitting on the eggs. The eggs usuallyhatch after about 15 days of incubation.
FIGURE 42-11
The adult mourning dove, Zenaida
macroura, stands about 30 cm (12 in.)tall and nests in trees or bushes.Mourning doves breed throughoutNorth America. They winter as far southas Panama.
FIGURE 42-12
853
CONNECTIONCONNECTION
Bird-Friendly Coffee Migratory songbirdpopulations are steadily declining in theUnited States and Canada. Species such asthrushes, warblers, and orioles typicallybreed in the north during the summer andspend winter in the tropical forests ofMexico, Central America, and CaribbeanIslands. Researchers suspect that a switchto a new method of growing coffee may be contributing to songbird decline.Traditionally, coffee has been grown on
REAL WORLDREAL WORLD
shade plantations, where the coffee plantsare grown under a canopy of planted trees.Over time, these plantations have becomeforest havens for wintering songbirds.However, coffee growers began planting newsun-tolerant coffee plants, which producemore coffee. As a result, the trees aroundthe coffee plants are being cut down and,scientists suspect, songbird winter homesare being lost.
ReteachingFlash Cards Have pairs of stu-dents prepare flash cards to helpthem learn the ten bird orderscovered in this section. On oneside of each card, have studentswrite the order name and sketcha representative bird from theorder. Have students refer to birdfield guides to make their draw-ings. On the other side of thecard, students should list infor-mation about the order. Let stu-dents spend some time drillingeach other using their cards, thenorally quiz them to see how muchthey were able to retain.
Verbal
QuizTrue or False:1.Birds are the most widespread
terrestrial vertebrates. (true)
2.The best way to tell a bird’shabitat is from the color of itsplumage. (false, a bird’s beak andfeet provide clues about its habitat)
3. Song birds use the syrinx toproduce songs. (true)
4.Most of the familiar songbirds belong in the order Passeriformes. (true)
GENERAL
Co-op LearningLS
Close
Answers to Section Review
1. Sample answer: The shape of a bird’s beak andfeet can help identify what the bird eats and theenvironment in which it lives. For example, hawksand eagles have powerful beaks and clawed talonsto help them capture and tear apart prey. Swiftshave beaks adapted to capturing insect in midair.The feet of flightless birds are modified for walking,running, or swimming.
2. dove: Columbiformes; robin: Passeriformes; goose:Anseriformes; penguin: Ciconiiformes
3. Raptors and owls are predators that have sharpbeaks and talons. Raptors are active during theday, and owls are active at night.
4. The syrinx produces sound.
5. Crop milk is a nutritious milklike fluid producedby the crop and used to feed the offspring ofcolumbiform birds.
6. Penguins swim with a motion similar to flying andthus need a keel-shaped sternum for the attachmentof their wing muscles. Ostriches neither fly nor swim,so they do not need a keel-shaped sternum.
7. Sample answer: Birds have feathers for insulationand are endothermic. The ability to fly also allowsthem to move long distances to other environmentswhen food is scarce or the climate is unsuitable.
8. Sample answer: Plant matter can be harder todigest than animal matter; hard seeds must becrushed to make them easier to digest.
854 C H A P T E R 4 2
Raptors have a sharp, curved beak and sharp talons and includeospreys, hawks, falcons, vultures, and eagles. About 310 species ofraptors are distributed throughout the world. Some members ofthis order grow to be quite large. Figure 42-13 shows a great blueheron, a large species that is in North America. The marabou storkof Australia, for example, can be more than 1.5 m (59 in.) in height.
Penguins are a unique group of flightless marine birds. All 17species live in the Southern Hemisphere. The penguin’s wedge-shaped wings have been modified into flippers, and the feet arewebbed. Underwater, penguins flap their flippers to propel them-selves forward—they “fly” through the water. Most penguins havea thick coat of insulating feathers and a layer of fat beneath theskin, enabling them to live in polar conditions. They maintain thisfat layer by consuming large quantities of fish and krill.
Order GalliformesMembers of this group, which includes turkeys, pheasants, chick-ens, grouse, and quails, are commonly called fowl. These terrestrialbirds are usually plump-bodied and may have limited flying ability.Grains form a large part of the diet of many fowl, and all specieshave a large, strong gizzard. Some are also an important part of thehuman diet. The young are precocial. There are about 220 speciesdistributed worldwide.
Order StruthioniformesSome of the world’s largest birds belong to this order. They includeostriches, rheas, emus, and cassowaries. Ostriches are native toAfrica and can attain a height of nearly 3 m and weigh 150 kg.Ostriches cannot fly, but they are specialized as high-speed run-ners. Propelled by their long, strong legs, ostriches can reachspeeds of 55 km per hour. Each large foot has only two toes.Reduction in the number of toes is common in running animals.
Rheas are a South American version of the ostrich. Emus are thesecond largest of the world’s birds, originally found in Australia.Cassowaries, from New Guinea, are the most colorful of this order,with black bodies and blue heads.
1. Explain how a bird’s beak and feet can provideinformation about the bird’s lifestyle.
2. Identify the order to which each of the followingbirds belongs: dove, robin, goose, and penguin.
3. Identify similarities and differences betweenraptors and owls.
4. Identify the function of the syrinx.
5. Describe the source and function of crop milk.
CRITICAL THINKING
6. Recognizing Relationships Penguins have alarge, keel-shaped sternum, but ostriches do not.Provide an explanation for this difference.
7. Analyzing Information Why can birds inhabitmore diverse environments than reptiles can?
8. Applying Information Why might crops andgizzards be less common in carnivorous birdsthan in seed-eating birds?
SECTION 3 REVIEW
syrinx
from the Greek syrinx,
meaning “reed” or “pipe”
Word Roots and Origins
The great blue heron, Ardea herodias,
uses its spearlike beak to stab fish,frogs, and other prey. Young heronsmust be taught how to hunt. Scientistshave learned that young herons oftenmiss their intended prey and must alsolearn what is and is not food.
FIGURE 42-13
854
AlternativeAssessmentAdaptations Have students workin groups and choose one birdadaptation. Groups should writea description of the adaptation andinclude illustrations. Post thesummaries and illustrations andhave each group describe theadaptation to the rest of the class.
Visual
Study TipObjectives Encourage studentsto copy the objectives for eachsection on a piece of paper. Havethem refer to the list as theystudy the chapter. When studentshave finished the chapter, havethem review the objectives again.
LogicalLS
GENERAL
Co-op LearningLS
GENERAL
B I R D S 855
Origin and Evolution of BirdsSECTION 1
CHAPTER HIGHLIGHTS
ClassificationSECTION 3
furcula (p. 842)
Vocabulary
syrinx (p. 853) crop milk (p. 853)
Vocabulary
feather (p. 844)follicle (p. 844)shaft (p. 844)vane (p. 844)barb (p. 844)
barbule (p. 844)preen gland (p. 844)sternum (p. 845)pygostyle (p. 845)crop (p. 846)
proventriculus (p. 846)gizzard (p. 846)vas deferens (p. 848)oviduct (p. 848)brood patch (p. 848)
precocial (p. 849)altricial (p. 849)ornithologist (p. 849)
Vocabulary
● Seven major characteristics of birds are feathers; wings;a lightweight, rigid flight skeleton; a respiratory systeminvolving air sacs; endothermy; a beak instead of teeth;and oviparity.
● Three similarities between birds and dinosaurs include anS-shaped neck, a unique ankle joint, and hollow bones.
● Archaeopteryx had feathers covering its body, tail, andforelimbs. It had hollow bones and a fused collar bone,called a furcula.
● There are two hypotheses for the origin of flight in birds.One hypothesis is that flight evolved in tree-dwellers. Thesecond hypothesis is that flight evolved in ground-dwellers.
Characteristics of BirdsSECTION 2
● Contour feathers are made of a central shaft composedof two vanes with branches, called barbs, that areconnected by interlocking hooked barbules.
● Two modifications to the bird skeletal system include anenlarged sternum and hollow bones.
● The crop stores food. The two parts of the stomach arethe proventriculus and the gizzard, which crushes food.
● The lungs of a bird are connected to several air sacs thatstore and move air but do not participate in gasexchange.
● Birds lack a urinary bladder and excrete their nitrogenouswaste as uric acid mixed with feces.
● The cerebellum, cerebrum, and optic lobes of the birdbrain are large.
● All birds lay hard-shelled eggs. Precocial young are activeas soon as they hatch. Altricial young are born helplessand require parental care for several weeks.
● Many birds migrate using a variety of environmental cuesto guide their migration.
● The feet and beak of a bird reflect its way of life.● There are currently 23 commonly recognized orders
of living birds, but technological advances add to our knowledge of relationships among animals, andtaxonomy is subject to change with new information.
● Ducks, geese, and swans belong to the order Anseriformes.● Owls are nocturnal hunters and belong to the order
Strigiformes.● Swifts and hummingbirds belong to the order Apodiformes.● Parrots and relatives belong to the order Psittaciformes.
● Woodpeckers and toucans belong to the order Piciformes.● Perching birds and songbirds belong to the order
Passeriformes. Passeriformes have a structure called thesyrinx, which they use to produce songs.
● Pigeons and doves belong to the order Columbiformes.● Raptors, long-legged water birds, and penguins belong to
the order Ciconiiformes.● Chickens and turkeys belong to the order Galliformes.● Large birds such as the ostrich belong to the order
Struthioniformes.
855
SECTION 0CHAPTER HIGHLIGHTS
to reduce weight
attached to lungs for streamlining
include
for lift with enlarged
Answer to Concept Map
The following is one possible answerto Chapter Review item 20.
adaptations for flight
flight feathersair sacs
hollowpygostyle
sternum contour feathers
urinary bladderurinary bladder
a bones that are lack of
for muscle attachment
keelkeel
TEACHER RESOURCES
Workbooks
• Study Guide• Vocabulary Review• Science Skills• Critical Thinking• Quizzes• Chapter Test• Chapter Test
Technology
Transparencies• Graphic Organizer• Concept Mapping
One-Stop Planner CD-ROM• Concept Mapping
Worksheet GENERAL
GENERAL
GENERAL
GENERAL
GENERAL
GENERAL
ANSWERS
Using Vocabulary1. a. The furcula is the fused collarbone,
the sternum is the breastbone. b. Flightfeathers are a specific type of contourfeather on the wings and tail that arespecialized for flight. c. The crop ispart of the esophagus and stores food,the gizzard is part of the stomachand grinds food. d. altricial young areborn helpless and require significantparental care. Precocial young areborn more developed and can walkand find food as soon as they hatch.
2. In males, sperm passes through thevasa deferentia into the cloaca. Infemales, the oviduct is where theeggs are fertilized by sperm.
3. Sample answer: Feathers, whichdevelop from a follicle and have ashaft with two vanes of barbs andbarbules, are cared for by preening,a process in which a bird rubs oilreleased from the preen gland intotheir feathers.
4. Sample answer: Precocial youngmature before they hatch. They areable to walk, swim, and feed them-selves when they hatch.
Understanding Key Concepts5. feathers; wings; lightweight, rigid
skeleton; endothermic metabolism;unique respiratory system; beak;and oviparity
6. teeth; claws on its forelimbs; andlong, bony tail
7. Archaeopteryx had feathers, wings,and a furcula.
8. One hypothesis is that birds evolvedfrom tree-dwelling dinosaurs thatused wings to glide between branches.The other states that birds evolvedfrom ground-dwelling dinosaurs thatused wings to glide when running andto capture prey.
9. Down feathers provide insulation, and contourfeathers give a streamlined shape.
10. The bones are light and hollow. Several bones arefused, making the skeleton rigid. The furcula andsternum are attachment points for wing muscles.
11. Sample answer: The crop stores and moistensfood. The gizzard kneads and crushes food.
12. gizzard13. Air sacs store oxygen-rich air and ensure that the
bird has oxygenated air in its lungs during bothinhalation and exhalation.
14. Ducks are precocial—they can swim, walk, andfeed themselves after they hatch. Pigeons arealtricial—they are helpless when they hatch.
15. position of stars or sun, landmarks, Earth’s mag-netic field, changes in air pressure, sounds
16. Raptors have strong, sharp beaks and sharptalons to capture and tear apart prey. Seed-eatingbirds have short strong beaks for cracking seedsand feet for perching. Flightless birds have feetmodified for walking and running.
17. ducks: Anseriformes; owls: Strigiformes; humming-birds: Apodiformes; parrots: Psittaciformes
18. syrinx19. They produce a milklike fluid called crop milk.20. The answer to the concept map is found at the
bottom of the Chapter Highlights page.
856 C H A P T E R 4 2
CHAPTER REVIEW
USING VOCABULARY1. For each pair of terms, explain how the meanings
of the terms differ.a. furcula and sternumb. flight feathers and contour feathersc. crop and gizzardd. altricial and precocial
2. Explain the relationship between vas deferentia,oviducts, and cloaca.
3. Use the following key terms in the samesentence: shaft, follicle, vane, barb, barbule,preening, and preen gland.
4. Word Roots and Origins The word precocial isderived from the Latin prefix pre-, which means“before,” and the term coquere, which means “tomature.” Using this information, explain why theterm precocial is a good word for the type ofyoung birds it describes.
UNDERSTANDING KEY CONCEPTS5. List the seven defining characteristics of birds.
6. Identify characteristics that Archaeopteryxshared with its dinosaur ancestors.
7. Summarize the evidence indicating thatArchaeopteryx could fly.
8. Compare two possible explanations for theevolution of flight.
9. Contrast the function of down feathers with thatof contour feathers.
10. Explain how a bird’s skeleton maximizes strengthfor flight while minimizing weight.
11. Describe the function of two organs that areunique to a bird’s digestive system.
12. Name the structure that grinds food, aided bystones that a bird swallows.
13. Describe the role that air sacs play in increasingrespiratory efficiency in birds.
14. Summarize the differences between newlyhatched ducks and newly hatched pigeons.
15. List several cues that birds might use to guidetheir movements when migrating long distances.
16. Explain the relationship between beak and feetshapes and the lifestyles of raptors, seed-eatingbirds, and flightless birds.
17. Identify the order to which each of the followingbirds belongs: ducks, owls, hummingbirds,parrots.
18. Name the characteristic that is unique to song-producing members of the order Passeriformes.
19. Explain how some members of the orderColumbiformes are similar to mammals.
20. CONCEPT MAPPING Use the following terms to create a concept map that
describes the adaptations of birds for flight:contour feathers, flight feathers, sternum, keel,pygostyle, hollow, urinary bladder, and air sacs.
CRITICAL THINKING21. Analyzing Concepts The right and left sides of
a bird’s heart are completely separated. Thus, the oxygenated blood is never mixed with thedeoxygenated blood. Why is this completeseparation in the heart necessary?
22. Interpreting Graphics Look at the diagram belowof a bird’s skeleton. Identify the following struc-tures: pelvic girdle, furcula, sternum, femur,humerus, ulna, and tibiotarsus.
23. Applying Information Why is binocular visionimportant to some birds?
24. Inferring Relationships Cowbirds lay their eggs in the nests of other birds. The young cowbirdshatch slightly earlier than the other birds do, andthe cowbird hatchlings are slightly larger. Whymight these characteristics be advantageous forthe young cowbirds?
25. Making Comparisons Although many species oftemperate-zone birds migrate to the tropics toescape winter, some species remain behind. What benefits might these birds gain from notmigrating?
26. Justifying Conclusions In terms of evolutionaryadaptations, explain why the young of somebirds, such as ducks and quail, are precocial.
A
B
CD
E
F
G
856
CHAPTER REVIEW
ANSWERS
B I R D S 857
Standardized Test PreparationDIRECTIONS: Choose the letter of the answer choicethat best answers the question.
1. Which of the following characteristics ofArchaeopteryx is not shared by modern birds?A. tailB. teethC. furculaD. feathers
2. Which of the following characteristics do birdsshare with dinosaurs?F. cropG. lack of teethH. presence of feathersJ. structure of the ankle joint
3. What is the function of the preen gland?A. to produce digestive enzymesB. to control salt balance in the body C. to release scents that help attract matesD. to produce an oily substance used to condi-
tion the feathers
4. Which bone supports the tail feathers?F. ulnaG. furculaH. pygostyleJ. pelvic girdle
INTERPRETING GRAPHICS: The graph below shows the effect of varying clutch size on the numberof surviving offspring in one bird species. Use thegraph to answer the question that follows.
5. Based on these data, which of the following state-ments is true for this species?A. The optimal number of eggs in a clutch is
seven.B. The greater the clutch size is, the greater the
number of surviving offspring.C. Nests with five eggs produced the fewest
number of surviving offspring.D. More offspring died in nests containing eight
eggs than in nests containing nine eggs.
DIRECTIONS: Complete the following analogy.
6. crop milk : crop :: song : F. syrinxG. tracheaH. proventriculusJ. anterior air sacs
INTERPRETING GRAPHICS: The diagram belowshows the digestive system of a bird. Use the diagramto answer the question that follows.
7. Which digestive structure grinds food, aided bystones swallowed by the bird?A. 1B. 2C. 3D. 4
SHORT RESPONSEEach type of feather on a bird serves a specificpurpose.
What are the functions of contour feathers and downfeathers in birds?
EXTENDED RESPONSEImagine that a museum display of bird skeletonsbecame mixed up, and all of the labels were lost.
Part A How could you separate the skeletons offlightless birds from those of birds that fly?
Part B How could you tell which birds flew rapidlyand which birds could soar?
When a question refers to agraph, study the data plotted on the graph to deter-mine any trends before you try to answer the question.
2
0
Nu
mb
er
of
surv
ivin
g o
ffsp
rin
g
Clutch size5 6 7 8 9
3
1
Effect of Varying Clutch Size
1
2
3
4
857
Critical Thinking21. Sample answer: A bird’s metabolism requires
a constant supply of oxygen. If the oxygenatedblood and deoxygenated blood mixed, therewould be less oxygen available.
22. A. ulna; B. humerus; C. furcula; D. sternum;E. tibiotarsus; F. femur; G. pelvic girdle
23. Sample answer: Birds such as raptors and owlsneed binocular vision to help them capture prey.Binocular vision gives them depth perception.
24. Because the cowbirds hatch earlier and are larger,they are more likely to be fed by the parents.
25. Sample answer: Migration requires a great dealof energy and can be dangerous. Also, if thebirds stay behind, they face less competitionfor remaining resources.
26. Sample answer: Many birds, such as ducks andquail, build their nests on the ground, where theeggs and young are at greater risk from predators.If the young are able to walk and swim right away,they can stay with their mother, and they can bemoved away from danger.
SECTION 0Standardized TestPreparation
Teaching TipTo provide practice under realistic test-ing conditions, give students 20 minutesto answer the Standardized TestPreparation questions.
1. B2. J3. D4. H5. A6. F7. B
Short ResponseContour feathers streamline the bird’sbody, and down feathers provide insula-tion.
Extended Response Part A Sample answer: Flightless bird
skeletons often do not have a keeledsternum. Also, the skeletons of flight-less birds may have a reduced numberof toes and may have a smaller number of hollow bones.
Part B Sample answer: Birds that couldsoar would have a wider wingspanthan birds that flew rapidly. Birds thatflew rapidly would have shorter wingswith respect to their body length.
Question 1 Students will likely recog-nize that all of the characteristics listedare found in Archaeopteryx. Some stu-dents may fail to recognize the trait thatis not characteristic of birds—teeth.Birds have a tail, a furcula, and feathers.Therefore, answer B is the best answer.
Question 5 Some students may be over-whelmed by the length of the answersand become confused. However, if students read the answers carefullyafter studying the graph, they should conclude that the ideal clutch size isseven. Otherwise, there are fewer surviving offspring. Therefore, answer Ais the best answer.
EXPLORATION LAB
Time RequiredOne 50-minute class period
Ratings
TEACHER PREPARATIONSTUDENT SETUPCONCEPT LEVELCLEANUP
Safety CautionsUse only feathers purchased from abiological supply house. Feathers from other sources, including featherscollected from the field, may containdangerous pathogens. Tell students notto touch their faces when they handlefeathers. Remind students that theyshould wash their hands with soap andwater as soon as they are finished withthe lab.
PreparationPrepare or purchase feather slides.
Materials and EquipmentUse the Lab Materials QuicklistSoftware on the Biology LabGenerator CD-ROM to create a customized list of materials for this lab.
Procedural Tips1. You may want to have students
prepare their data collection tablesahead of time.
2. Turn off room fans or close windows to prevent breezes from blowing thefeathers around the room.
E A SY HAR D
Answers to Background
1. Birds have feathers, wings, hollow bones, a furcula, a rigid skeleton, and a beak. They lay hard-shelled eggs, have wings, are endothermic,and have a unique respiratory system that keepsoxygenated air in their lungs at all times.
2. Birds have feathers, hollow bones, a proventriculusand gizzard, a crop, and lack teeth.
3. Feathers enable birds to fly and insulate them fromheat loss. Colorful feathers on some birds providecamouflage or advertise for a mate.
858 C H A P T E R 4 2
Comparing Feather Structureand Function
■ Observe a flight feather, a contour feather, and adown feather.
■ Compare the structure and function of different kindsof feathers.
■ safety goggles, lab apron, protective gloves■ 1 quill feather (large flight feather from wing or tail)■ 1 contour feather■ 1 down feather■ unlined paper■ prepared slide of a contour feather■ compound light microscope■ prepared slide of a down feather
Background
1. List several distinguishing characteristics of birds.2. How do birds differ from other vertebrates?3. What are the functions of feathers?
Procedure
1. In your lab report, make a table like the one on thenext page. Record your observations of each kind offeather in your data table.
2. Put on safety goggles, a labapron, and disposable gloves.
Examine a quill feather. Hold the base of the centralshaft with one hand, and gently bend the tip of thefeather with your other hand. Be careful not tobreak the feather. Next, hold the shaft, and wavethe feather in the air. Record your observations con-cerning the structure of the quill feather. Relate yourobservations to the feather’s possible function.Describe the function of the feather under “Functionof feather” in your data table.
3. Examine the vane of the feather. Does the vaneappear to be a solid structure? Include a descriptionof the quill feather’s vane structure under “Structureof feather” in your data table.
4. Make a drawing of the quill feather. Label the shaft,vanes, and barbs. Compare your feather with thefigure above.
5. Examine a contour feather. Make a sketch of thecontour feather in your data table. Label the shaft,vanes, and barbs on your sketch. Does the featherresemble the one in the figure on the next page?
6. Describe the structure of the contour feather under“Structure of feather” in your data table.
7. Examine a prepared slide of a contour feather underlow power. Note the smaller barbs, called barbules,extending from each of the barbs.
8. How might you observe the region between thebarbs? Locate the tiny hooks at the end of each bar-bule. Note the arrangement of the hooks on adja-cent barbs. Why do you think the hooks are sosmall? Make a separate, labeled drawing of thehooks in your lab report.
9. Examine the down feather, and sketch it in yourdata table. How does your down feather comparewith the figure on the next page?
10. Describe the structure of the down feather in yourdata table. Do you notice a difference in the struc-ture of the contour and down feathers?
SAFETY
MATERIALS
OBJECTIVES
EXPLORATION LAB
Quill feather, a large flight feather
858
TEACHER RESOURCES
Workbooks
Datasheets for In-Text Labs• Comparing Feather Structure and
Function
Skills Practice Labs• Conducting a Bird Survey GENERAL
GENERAL
Answers to Analysis and Conclusions
1. The shaft is the central structure of thefeather, where the barbs areattached. The barbs are the sidebranches that extend from the shaft.A vane is a group of barbs on oneside of the feather shaft. The barbsand vanes make up the main body ofthe feather.
2. Sample answer: Hooks interlock onthe feather and keep spaces fromdeveloping between the barbs. Bykeeping the area between the barbsunbroken, the feather provides airresistance by diverting the air aroundthe feather rather than through it.
3. Sample answer: The shape andstrength of the quill feathers enable abird to catch the air during flight.
4. Sample answer: Down feathers can trap more air, providing moreinsulation.
5. Sample answer: Down featherswould be closest to the skin to pro-vide insulation. Contour featherswould cover the down feathers tomake the bird’s body streamlined.Flight feathers would be on the wingsand tail. The feathers would be orientedso that they point backward relativeto the desired direction of travel.
6. Answers may vary. Accept any answerthat cites natural selection as a reason for the evolution of down,contour, and quill feathers.
Answers to Further InquiryAnswers may vary. Students shouldnote that the fluffy shape of down feathers traps more air than a smoothfeather would. The smooth shape ofcontour feathers helps reduce windresistance when flying. The strong, rigid shape of flight feathers helps themcatch wind and provide lift.
B I R D S 859
COMPARISON OF FEATHERS
Type of feather Sketch of feather Structure of feather Function of feather
Quill feather
Contour feather
Down feather
11. Examine the prepared slide of the down feather underlow power. Locate the barbs and barbules. Switch yourmicroscope to high power, and make a separate,labeled drawing of the down feather in your labreport. Does it resemble the one in the figure above?
12. Clean up your materials, and wash yourhands before leaving the lab.
Analysis and Conclusions
1. What is the function of the shaft? What is the functionof the vanes and barbs?
2. How do hooks increase the strength and air resistanceof a feather?
3. How is the structure of the quill feather related to itsfunction of aiding flight?
4. Based on your observations, why might down feathersbe more effective at keeping a bird warm than theother two feather types you observed?
5. Based on your observations, how do you expect to seethese feathers arranged on a bird? Explain how posi-tion of the feather affects the function of the feather.
6. What evolutionary pressure(s) would have caused theevolution of these different types of feathers?
Further Inquiry
Each of the feather types you have examined has a specificstructure and function. Review your observations, and tryto think of features that account for the efficiency of thethree types of feathers.
Contour feather
Down feather
859
