ADVANCED LEC 14ORNITHOLOGY

University of Rio GrandeDonald P. Althoff, Ph.D.

Migration &Navigation – Part II

Reference Chapter 10

Learning About Migration & Navigation• Pfeilstorch = German for “arrow

stork”. Name given to storks injured by an arrow while wintering in Africa…then returning to Europe. Most famous Pfeilstorch found in 1822 in a German village—it was carrying an arrow from central Africa in its neck. This specimen was stuffed and is in a collection at the University of Rostock…and is known as the Rostocker Pfeilstorch.

Homing & Navigation• German study of storks:

a) held back juvenile storks until adults had migrated

b) RESULTS: juveniles traveled stork’s migration route. Therefore, for this species, ______________ to navigate/migrate.

• English study of mallards:a) took eggs from mallards that nested in

England and were non-migratory popn

b) hatched the eggs 1,500 miles to the northc) hatched mallards __________ even thoughthey were non-migratory.

Manx Shearwaters: Homing Studies

• Displaced 338 individuals returned home from long distances with remarkable promptness—i..e, displayed remarkable _________ ability

• One bird, displaced from Skokholm, Wales, UK and taken to Boston returned in 12 ½ days…averaging 250 miles per day…traveling minimum of 3,050 miles

Laysan Albatrosses: Homing Studies

• 18 adults shipped via air from nest sites in Midway Atoll to 6 different locations around the North Pacific Ocean

• 14 of 18 (representing at least 1 from each release location) returned to Midway Atoll—the farthest was 4,120 miles in 32 days

Penguins: Homing Studies

• Adelie penguins breed on exposed rock all around the Antarctic continent. At least 177 separate sites = rookeries.

• Adelie penguins were displaced long distances in all directions from natal rookeries

• All returned home, even if it meant swimming around large areas of land mass

How Do These Birds Navigate?

• Sun

• Influence of topography and/or landmarks

• Magnetic field / Geomagnitism

• Celestial bodies = sun, stars, moon, planets…known collectively as celestial cues

Sun• Greater efficiency of homing with clear skies—

during cloudy conditions, random homing• Clock shifting: depends on bird’s innate knowledge

of where sun will be. Experiments show if off 6 hours, homing off 90o

• More recent study of yellow-faced honeyeater suggest that sun is usually used as a “__________ ______” in combination with the magnetic field

See: Munro, U. and R. Wiltschko. 1993. Clock-shift experiments with migratory yellow-faced honeyeaters, Lichenostomus chrysops

(Meliphagidae), an Australian day-migrating bird. Journal ofExperimental Biology 181:233-244. (available on email request)

Topography or Landmarks

• _______________ birds get back home better than inexperienced birds

• Best homing at distances of _____ miles. For these same birds homing success increased at 30-40 miles away…perhaps then using sun and electromagnetic fields.

• _______ routinely follow highways, railways, and rivers—even if not the most direct route.

• Waterfowl known to follow watercourses and coastlines—but reluctant to cross large, open bodies of water unless favorable winds.

Some Celestial Cue Theories (handouts)

• _________ Azimuth Theory—studied starlings in caged environment. On cloudy days, no directional tendencies…but clear days focused correct direction for spring migration

• _________ Sun Arc Theory—studied homing pigeons released from unfamiliar sites…under varying weather conditions. When birds could see sun, they flew directly home.

• _________ Navigation by Northern Stars Theory—planets least likely cue, moon only visible part of month…so fixed on stars.

• …then Steve Emlen’s classic studies!

____________: Ph.D. studiesat Cornell University

• Examined orientation behavior of ______________ my manipulating the location and movements of stars and constellations in a planetarium.

• Determined they derived ______________ information from the pattern of constellations relative to each other and the celestial pole

Birds viewed the ‘_____’ through the screen… the starswere “set” both aligned and inproperly alignend

Emlen’s studies of indigo buntings…con’t

Effects of _______________…restlessness!

“Footprint” record Resulting Vector Diagram

Emlen’s studies of indigo buntings…con’t

Celestial Cue Theories….• Despite some “challenges”, the earlier theories (i.e.,

work) by Kramer, Matthews, and Sauers remain plausible to varying degrees

• There is evidence—especially based on Emlen’s research—that birds ____ orient by sun, by stars…even using some of both

• Magnetism, as proposed by Keeton, could serve as a backup system to sun or star navigation when neither of the later are “available”.

Magnetic Field Orientation

Evidence:A) Pigeons disoriented

wearing bar magnetsB) Robins in steel cages,

when magnetic field is reversed , reversed Zugunruhe

C) Pigeons with “electric cap” fly in opposite direction

D) Iron-rich sensory neurons found in pigeon’s skull

http://www.livescience.com/33889-pigeons-gps-cells-strange-snapshots.html

Magnetic Field Orientation…con’t

• Conclusion on MAGNETIC orientation: bird’s can and do judge compass direction by sensing the Earth’s magnetic field. However, this is more important in young birds and….

…as they mature, celestial cues (sun and stars) become the more important compass reference

In Summary….• Billions of birds migrate every fall and spring to exploit

a) _______________ opportunities and b) ____________ opportunities

• Exactly why some species migrate and others do not is somewhat still an unresolved question

• Flights of many long-distance migrants require extraordinary ___________________

• Conservation of migrant species is of concern—as many populations are declining. The problem can be due to loss of suitable a) ________ habitat in Central and the Caribbean and b) ________ grounds in North America

• Birds use different sources of info to navigate