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, 273 (1603), 2815-20

Bird Navigation: What Type of Information Does the Magnetite-Based Receptor Provide?

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Bird Navigation: What Type of Information Does the Magnetite-Based Receptor Provide?

Wolfgang Wiltschko et al. Proc Biol Sci.

Abstract

Previous experiments have shown that a short, strong magnetic pulse caused migratory birds to change their headings from their normal migratory direction to an easterly direction in both spring and autumn. In order to analyse the nature of this pulse effect, we subjected migratory Australian silvereyes, Zosterops lateralis, to a magnetic pulse and tested their subsequent response under different magnetic conditions. In the local geomagnetic field, the birds preferred easterly headings as before, and when the horizontal component of the magnetic field was shifted 90 degrees anticlockwise, they altered their headings accordingly northwards. In a field with the vertical component inverted, the birds reversed their headings to westwards, indicating that their directional orientation was controlled by the normal inclination compass. These findings show that although the pulse strongly affects the magnetite particles, it leaves the functional mechanism of the magnetic compass intact. Thus, magnetite-based receptors seem to mediate magnetic 'map'-information used to determine position, and when affected by a pulse, they provide birds with false positional information that causes them to change their course.

Figures

Figure 1
Figure 1
Orientation of silvereyes in the geomagnetic field before pulse treatment. The arrows represent the mean vectors of the 24 individual test birds based on six recordings each; the triangles outside the circle mark the respective mean headings.
Figure 2
Figure 2
Orientation of silvereyes immediately after the pulse and on the following two evenings. The triangles at the periphery indicate the individual headings of the 24 birds and the arrows represent the mean vectors under the different magnetic conditions. The two inner circles give the 5% (dashed) and the 1% significance border of the Rayleigh test (Batschelet 1981).
Figure 3
Figure 3
Model illustrating the use of magnetic information obtained by different types of receptors in different parts of the navigational system.

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