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Compass orientation in migratory birds

Birds use a number of different compasses based on the geomagnetic field, stars, the sun and the related pattern of skylight polarization for orientation. In a series of cue-conflict experiments performed with birds captured in southern Scandinavia and North America we have analysed the effect of conflicting visual and magnetic information for compass-calibration. The results from these experiments, suggest interesting differences (no recalibration) in the way birds respond to cue-conflict situations in Europe that differ from previous studies with songbirds in North America.

In further studies, we will investigate the effect of cue-conflict situations to birds’ orientation, and include measurements of the polarized light conditions during exposure. A rather sensitive sensory system is required to detect the low (< 10%) degrees of polarisation transmitted, and we do not yet know if birds possess such a sensitive system. We will also perform simulated magnetic and real displacements to study the use of a map vs. clock-and-compass model for orientation during first and later migrations, but also to investigate how the expression of the birds endogenous migration program are affected by external magnetic information. Adult (experienced) and young (migratory naïve) songbirds will be compared.

The Emlen funnel

Emlen funnels
Photo: Susanne Åkesson

Jannika Boström is preparing orientation cages, so called Emlen funnels, for studies of orientation in Northern Wheatears on Arctic Ocean sea ice. The bottom of the cage is lined with Tipp-ex paper, on which the bird leaves scratchmarks when trying to fly off. These marks give us an indication of what direction the bird is heading at.

Ongoing orientation experiment

Bird in a funnel
Photo: Michaela Illieva

The scratches on the soft Tipp-ex paper shows the bird´s migration direction. These papers can be analysed by circular statistic. Here, a dunnock (Prunella modularis) is studied within an orientation cage.

Arctic expedition

Arctic expedition
Photo: Swedish Polar Research Secretariat.
Susanne Åkesson is initiating orientation cage experiments on the Arctic Ocean sea ice during a Swedish expedition to the North Pole in 2005.
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Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
Ecology building S-223 62 Lund Sweden