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Audrey Dods

84ba8d1eb2aeb6ea03155d37fef788a1?s=47 Audrey
October 12, 2020

Audrey Dods

It's estimated that one in five birds is migratory, moving from a Northern range to a Neotropical range in the winter to breed and access resources. But how do they know where to go? This presentation dives into the literature surrounding avian navigation and includes interactive resources for further information.

84ba8d1eb2aeb6ea03155d37fef788a1?s=128

Audrey

October 12, 2020
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Transcript

  1. Navigation: Origins, Patterns, and Mechanisms Audrey Dods

  2. Origins of Migration • Hypothesis: Migration evolved out of tropics

    via shifts of breeding ranges • Result: Seasonal migration evolved more often via shifts in winter ranges towards the Neotropics from North America (Winger et al. 2014) Pink lines indicate neotropical migration, a lineage starting out in North America or the tropics and evolving to a Neotropical migratory condition by the end of its branch (Winger et al. 2014)
  3. Migration Patterns • Migratory birds show breeding site fidelity ◦

    Breeding site fidelity- returning within a short distance of a migratory destination after wintering thousands of miles away (Sokolov 1991) Bird Superhighways: Major flyaways contain suitable habitats in which migrating birds can rest and forage between their breeding and wintering grounds Graphic from: https://www.birdlife.org/worldwide/progr ammes/migratory-birds
  4. Migration Patterns (cont.) • Migratory birds have shown incredible homing

    abilities ◦ Many seabirds even locate small islands with no landmarks Starlings returned to nest after being released 500 miles away Swallows returned to nest after being released 1,100 miles away Manx shearwaters crossed the Atlantic for 3,050 miles in 12.5 days Laysan albatrosses returned after 3,200 miles in 10.1 days
  5. Case Study: Small Songbirds • Millions of songbirds migrate to

    Central and South America every year ◦ Results in a huge calorie loss if traditional flyaways are followed • Songbirds loop across the continent during migration (Sorte et al. 2014) ◦ Stronger tailwinds in spring, less severe headwinds in fall ◦ Take advantage of seasonal weather and food patterns • Migrant traps ◦ Areas where large numbers of birds gather to rest and feed ◦ Tired songbirds flying over Gulf States collect in live oak groves, collecting in a “fallout” Baltimore Oriole, Indigo Bunting, Chestnut-sided Warbler, Bay-breasted Warbler, Blue Grosbeak, Scarlet Tanager, Black-throated Green Warbler, Orchard Oriole, Black-and-white Warbler, Blackburnian Warbler
  6. Navigation Mechanisms • Only true navigation could explain the incredible

    migration patterns of birds ◦ True navigation- finding the goal of migration without direct sensory contact with it (Chernetsov 2016) • Map and compass concept ◦ Assumes that migrating birds first orient themselves in relation to their goal (map) and then maintain a direction of movement towards the goal (compass) (Kramer 1953, 1957, 1961) ◦ Must understand the nature of the map and the nature of the compass
  7. Compass System • Orientation- the ability to use the compass

    system; to select and maintain a certain compass direction (Chernetsov 2016) • Three possible mechanisms: ◦ Solar (learned) ▪ Based on regular movement of sun across the sky ▪ Time-dependent; shifting a bird’s internal clock by 1 hour offsets solar compass by 15° ◦ Stellar (learned) ▪ Based on orientation of stars in the sky and bird’s internal clock ▪ Indigo buntings used constellations to determine geographic North (Emlen 1967) ◦ Magnetic (innate) ▪ Detection of geomagnetic compass information through light-dependent chemical reactions in the retina, allowing birds to “see” magnetic fields
  8. Case Study: Indigo Buntings • Methods ◦ Emlen funnels w/

    ink pad and paper walls allow detection of movement ◦ “Stars” manipulated inside a planetarium ◦ Different patterns of constellations were tested at varying times during the night and day • Results ◦ Constancy of direction during different times of the night ◦ Suggests a reliance upon a time-compensating orientational system (similar to solar hypothesis) ◦ Birds alters its angle of orientation in relation to the stars at a rate which compensates for the movement of celestial objects (recognize patterns) (Above) Light pollution impacts the navigational skills of Indigo Buntings (Below) A typical Emlen funnel setup
  9. Magnetic Field: A “Sixth Sense” • Cry4 proteins in eyes

    stay constant throughout the day ◦ Birds must need to produce these proteins consistently • Electrons on Cry4 are excited by photons • These electrons interact with the Earth’s magnetic field
  10. Navigational Maps • Navigation- the ability to use the map

    system; to detect the position of the goal of movement without direct sensory contact with the goal (Chernetsov 2016) • Possible mechanisms: ◦ Olfactory ▪ Use of smell to build a spatial map/reference ▪ Homing pigeons deprived of olfactory information navigated poorly (Gagliardo 2013) ▪ Criticized for availability of smells in atmosphere ◦ Magnetic ▪ Migratory birds build a gradient map based on total intensity and magnetic inclination between the Earth’s magnetic poles ◦ Less conventional mechanisms ▪ Coriolis force (antiquated), gravitational anomalies, infrasound, astronomical navigation
  11. Case Study: Homing Pigeons • Methods ◦ Olfactory nerves compromised

    by spraying local anesthetic into nostrils ◦ Released from an unfamiliar site ◦ Sometimes deprived of smells on the way to the site • Results ◦ Pigeons could orient themselves if exposed to smells on the way to the release site ◦ No exposure to olfactory senses left pigeons disoriented ◦ Olfactory map built on wind-borne odors and the direction they come from (Above) Pigeons follow familiar odor dispersions to get home
  12. Migration Resources • Check out daily migration forecast maps at

    https://birdcast.info/ !
  13. Citations Primary Literature Chernetsov, N.S. 2016. Orientation and navigation of

    migrating birds. Biology Bulletin 43: 788-803. Emlen, S.T. 1967. Migratory orientation in the indigo bunting, Passerina cyanea. Part II: Mechanism of celestial orientation. Auk 84: 463–489. Gagliardo, A. Forty years of olfactory navigation in birds. Journal of Experimental Biology 216: 2165-2171. Kramer, G. 1953. Is the height of the sun used in homing orientation? Journal of Ornithology 94: 201–219. Kramer, G. 1957. Experiments in bird orientation and their interpretation. Ibis 99, no. 2: 196–227. Kramer, G. 1961. Long-distance orientation. Biology and Comparative Physiology of Birds: 341-371. La Sorte, F.A., D. Fink, W.M. Hochachka, A. Farnsworth, A.D. Rodewald, K.V. Rosenberg, B.L. Sullivan, D.W. Winkler, C. Wood & S. Kelling. 2014. Journal of Biogeography 41: 1685- 1696. Sokolov, L.V. 1991. Phylopatry and dispersion of birds. Zoologicheskii Zhurnal 63: 1671-1681. Winger, B.M., F.K. Barker & R.H. Ree. 2014. Temperate origins of long-distance seasonal migration in New World songbirds. Proceedings of the National Academy of Sciences 33: 12115-12120. Additional Resources https://www.britannica.com/science/migration-animal/Navigation-and-orientation https://www.allaboutbirds.org/news/the-basics-how-why-and-where-of-bird-migration/ https://www.birdlife.org/worldwide/programmes/migratory-birds http://www.ks.uiuc.edu/Research/cryptochrome/ https://www.audubon.org/magazine/march-april-2015/star-trek-how-birds-use-electromagnetic-cues