Avian Reproduction

Nests, Eggs, and Chicks

With emphasis on differences in chick development

Scrape nests are simple depressions in the ground (sometimes with a few stones added) or in the leaf litter. Such nests are used by some penguins, shorebirds, gulls, terns, nighthawks, vultures and other species.

Burrow nests are very effective at protecting eggs and young from predators & maintaining an appropriate microclimate for eggs & young. Some birds, like Bank Swallows and Belted Kingfishers (pictured below), usually construct their own burrows, while others, such as Burrowing Owls, may use burrows constructed by other species.

Cavity nests (e.g., in trees or cacti) are used by numerous passerines, woodpeckers, owls, parrots, and some waterfowl. Some birds, such as woodpeckers, construct their own cavity nests and are referred to as primary cavity nesters. Species that use natural cavities or cavities constructed by primary cavity nesters are called secondary cavity nesters.

Platform nests are relatively flat nests that may be located on the ground, in a tree, or on the tops of rooted vegetation or debris in shallow water like the Western Grebe nest below).

Cupped nests are, of course, cup-shaped. Such nests may be constructed of various materials and in a variety of locations. Pettingill (1985) categorized cup nests as follows:

statant cupped nests - nests located in the crotches and branches of trees and shrubs and supported mainly from below. Many passerines and hummingbirds build such nests.

suspended cupped nests - nests not supported from below but from the rims, sides, or both:

pensile - nests suspended from the rims and sides; rather stiff, e.g., those of kinglets and vireos (like the Black-capped Vireo pictured below)

pendulous - nests suspended from the rims and sides; rather flexible and deep, like those of orioles

adherent nests - cupped nests whose sides are attached by an adhesive substance (e.g., mud or saliva) to a vertical surface, like those of swifts and some swallows (see Barn Swallow nest below)

ground nests - cupped nests on the ground; sides are sometimes extended upward and arched over the top making a domed structure. Several passerines, particularly those that occupy open habitats like grasslands and tundra, build ground nests.

Veery Louisiana Waterthrush

Colonial nests of the Sociable Weaver – Protection from snakes (cobras) Thermoregulation Nesting associations with Pygmy Falcons

Lesser-masked weaver

white-browed sparrow weaver

Village Weaver, Ploceus cucullatus,Weaving a single strip of elephant grass.After Collias and Collias 1962.

Various knot types used by Weavers

Tailorbird

Tits weave fragrant nests. - Birds weave aromatic plants into their nests, apparently to keep their home clean and bug-free for raising chicks. Blue Tits on the fragrant Mediterranean island of Corsica can even smell when it's time to refresh fading fragments, ecologists have shown (Petit et al. 2002). Female blue tits gather lavender, yarrow, curry, mint and other scented plants for their nests shortly after laying eggs, and continue to do so until the chicks leave home. "They are real botanists and do a great job exploiting their environment to protect their chicks," says Marcel Lambrechts of the Centre for Functional Ecology and Evolution in Montpellier, France. The birds make a pot-pourri of 10 aromatic plants from the 250 species in their habitat. Many of the chemicals in these plants ward off bacteria, viruses, parasites, fungi and insects. Lambrechts's team removed the aromatic plants from 64 nests and then placed a hidden box containing lavender and yarrow underneath half of the nests. In the first 24 hours, only the birds with empty boxes replenished their herb supply. After 48 hours, the other half of the birds began to restock too, as the scent from the hidden herbs waned. "This field test directly shows that birds are attending to odour cues," says Larry Clark, who studies similar behaviour  in European Starlings at the National Wildlife Research Center in Fort Collins, Colorado. The Blue Tits select for chemical diversity as well as high concentrations of chemicals, he points out, underlining the importance of olfaction in avian behavior.

Camouflage in the Pied Monarch

(a) Lined forest falcon(b) Hoatzin(c) Great Antshrike

(d) Martins(e) Woodpeckers(f) Tityras(g) Parakeets

(h) Sulphur-rumped Flycatcher

(i) Little hermit

(j) Blue-crowned motmot ((k) Olive-backed foliage- gleaner

(l) Bluish-fronted Jacamar

(m) Chestnut-capped Puffbird

(n) Starred wood-quail

Common Murre eggs Blue Tit

Regent Bowerbird

Azure Kingfisher

Pied Oystercatcher

Parental Care:

Incubation/broodingFeedingDefense

At hatching, some young birds are entirely dependent on their parents, while others are able to leave the nest and begin finding their own food within hours of hatching. Based on such differences, young birds are generally categorized as either altricial or precocial. Because of variation within these two broad categories, ornithologists more precisely classify young birds into six categories (Gill 1995):

superprecocial young are completely independent at hatching; no parental care

examples include young megapodes

Malleefowl

precocial young leave the nest soon after hatching and follow parents

young can feed themselves almost immediately examples include young waterfowl, shorebirds, and gallinaceous birds

Dunlin

subprecocial young leave the nest at hatching and follow parents

young are fed by parents (or at least shown where food is located by parents) examples include young rails, grebes, & loons

Eared Grebe

semiprecocial young are somewhat mobile at hatching but remain & are fed by their parents

examples include young gulls and terns

Common Tern

semialtricial young not mobile at hatching & are fed and brooded by parents

eyes of young open at hatching (semialtricial 1) or within a few days (semialtricial 2, e.g., owls )

examples include young herons, hawks, & owls

altricial young are naked, blind (eyes closed), & helpless at hatching

examples includes songbirds, woodpeckers, hummingbirds, and pigeons

Summary of characteristics of young birds at hatching (Nice 1962):

Type of  Developmen

t

Down  present

Eyes  open

MobileFeed

ThemselvesParents present

Examples

Superprecocial Yes Yes Yes Yes No megapodes

Precocial Yes Yes YesYes (follow

parents & find own food)

Yeswaterfowl, shorebirds

Subprecocial Yes Yes YesYes (may be shown food by parents)

Yes

grebes, rails,

cranes, & loons

Semiprecocial Yes YesYes, but remain in

nestNo Yes

gulls & terns,

penguins

Semialtricial 1 Yes Yes No No Yeshawks,

herons & egrets

Semialtricial 2 Yes No No No Yes owls

Altricial No No No No Yes songbirds