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Orientation of Snow Buntings (Plectrophenax nivalis) close to the Magnetic North Pole

Författare:
Publiceringsår: 1998
Språk: Engelska
Sidor: 1859-1870
Publikation/Tidskrift/Serie: Journal of Experimental Biology
Volym: 201
Nummer: 12
Dokumenttyp: Artikel i tidskrift
Förlag: The Company of Biologists Ltd

Sammanfattning

Orientation experiments were performed with first-year

snow buntings (Plectrophenax nivalis) during their autumn

migration in a natural near-vertical geomagnetic field

approximately 400 km away from the magnetic north pole.

Migratory orientation of snow buntings was recorded using

two different techniques: orientation cage tests and freeflight

release experiments. Experiments were performed

under clear skies, as well as under natural and simulated

complete overcast. Several experimental manipulations

were performed including an artificial shift of the E-vector

direction of polarized light, depolarization of incoming

light and a 4 h slow clock-shift experiment. The amount of

stored fat proved to be decisive for the directional

selections of the buntings. Fat individuals generally chose

southerly mean directions, whereas lean birds selected

northerly headings. These directional selections seemed to

be independent of experimental manipulations of the

buntings’ access to visual cues even in the local near-vertical

magnetic field. Under clear skies, the buntings

failed to respond to either a deflection of the E-vector

direction of polarized light or an experimental

depolarization of incoming skylight. When tested under

natural as well as simulated overcast, the buntings were

still able to select a meaningful mean direction according

to their fat status. Similarly, the free-flight release test

under complete overcast resulted in a well-defined

southsoutheast direction, possibly influenced by the

prevailing light northwest wind. Clock-shift experiments

did not yield a conclusive result, but the failure of these

birds to take off during the subsequent free-flight release

test may indicate some unspecified confusion effect of the

treatment.

Nyckelord

  • Biological Sciences
  • bird
  • migration
  • orientation
  • magnetic north pole
  • Plectrophenax nivalis
  • snow bunting

Övriga

Published
  • ISSN: 1477-9145

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