Lund University
Animal Ecology Department of Ecology Lund University

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Migration Ecology

Orientation


 

Birds seem to have a sixth sense to find their way on the wide-ranging journeys. Intensive research during the two recent decades has expanded knowledge about birds' compass mechanisms greatly, and it has been demonstrated that they rely on several different cues - the geomagnetic field, sun, sunset, skylight polarization pattern and stars - for their orientation. Still, we have little understanding how they actually orient when traveling on migration, what is the relative importance of different cues in the birds' orientation systems, and how the different compass mechanisms interact.

Our research is focused on the ecological aspects of bird orientation, and we try to find out if birds adapt their orientation and use of different cues depending on their fuel condition and migratory situation. We have indeed demonstrated a profound difference in orientation behaviour between fat and lean birds captured on migration. We have also carried out extensive orientation cage experiments with manipulations of the magnetic field, sky visibility and skylight polarization, comparing the responses of different species. Such experiments have been conducted close to the Magnetic North Pole in arctic Canada, in Greenland, at the northern tundra in Siberia and close to the equator in Kenya, to investigate how birds cope with the special difficulties of orientation at these places. We have a close collaboration with the bird observatories at Falsterbo and Ottenby for our orientation research programme in Sweden. In addition to cage experiments, release experiments, radio telemetry, as well as radar and satellite tracking are recurrent methods in our orientation research.

Cage view

Coil

Current studies include experiments on the light dependent magnetic orientation in birds and radar studies on free flying birds. Successful modifications of the orientation cage technique open up long-awaited possibilities of comparing the orientation responses of waders with existing results for many passerine species. Other ongoing experiments deal with the intercalibration of different compass mechanisms during the birds' ontogeny, and with the importance of the wavelength of monochromatic light for the orientation capacity with and without access to the normal geomagnetic field.

Quite another type of approach is to examine travel routes and flight paths (as recorded by radar and satellite tracking) in the light of various predictions, based on different possible orientation mechanisms, about courses and course changes. Flight routes are particularly revealing in polar regions where the birds meet special difficulties in orientation and where great circle orientation is of highest significance (see also migration patterns ). Preliminary results, which indicate that waders in northernmost Siberia may orient close to great circle routes while this is not the case for brent geese flying across Greenland, inspire to continued investigations.

Primary projects: Susanne Åkesson, Thomas Alerstam

Graduate programmes: Oskar Brattström, Johanna Grönroos

Other researchers: Johan Bäckman, Rachel Muheim, Kasper Thorup

A few selected publications:

  • Åkesson, S. & Hedenström, A. Selective flight departure in passerine nocturnal migrants. - Behav. Ecol. Sociobiol. 47:140-144.
  • Åkesson, S., Morin, J., Muheim, R. & Ottosson, U. 2001. Avian orientation at steep angles of inclination: experiments with migratory white-crowned sparrows at the magnetic North Pole. - Proc. R. Soc. Lond. B. 268:1907-1913.
  • Alerstam, T. 1996. The geographic scale factor in orientation of migrating birds. - J. Exp. Biol. 199:9-19.
  • Bäckman, J. & Alerstam, T. 2001. Confronting the winds: orientation and flight behaviour of roosting swifts, Apus apus. - Proc. R. Soc. Lond. B 268:1081-1087.
  • Luschi, P., Åkesson, S., Broderick, A. C., Glen, F., Godley, B. J., Papi, F. & Hays, G. C. 2001. Testing the navigational abilities of ocean migrants: displacement experiments on green turtles (Chelonia mydas). - Behav. Ecol. Sociobiol. 50:528-534.
  • Sandberg, R., Bäckman, J., Moore, F. R. & Lohmus, M. 2000. Magnetic orientation calibrates celestial cues during migration. - Anim. Behav. 60:453-462.
  • Thorup, K., Alerstam, T., Hake, M. & Kjellén, N. 2003. Bird orientation: compensation for wind drift in migrating raptors is age-dependent. - (Biology Letters) Proc. R. Soc. Lond. B (suppl) 270:S8-S11.