Medical/biological study (experimental study)

Not all songbirds calibrate their magnetic compass from twilight cues: a telemetry study med./bio.

By: Chernetsov N, Kishkinev D, Kosarev V, Bolshakov CV

Published in: J Exp Biol 2011; 214 Pt 15: 2540-2543

Aim of study (acc. to author)

Migratory birds are able to use the sun and associated polarised light patterns, stellar cues and the geomagnetic field for orientation. No general agreement has been reached regarding the hierarchy of orientation cues.
In this study the hypothesis was tested, 1) whether the magnetic compass is calibrated from twilight celestial cues, 2) either magnetic or stellar cues are used separately without transferring reference information to others (simple domination) or 3) whether the stellar compass is calibrated from the magnetic field.

Background/further details

All song thrushes were captured during the autumn and spring passage in Rybachy, Kaliningrad Region, Russia. In autumn, only hatching-year birds were tested and in spring, only second calendar year birds were included. Birds were released at two different locations to test whether they used landmarks or global cues (solar, stellar or geomagnetic). All birds were radio tagged and could be followed for at least 15 km. Birds were exposed one hour before sunset and released when the sun was 12° below the horizon.

Endpoint

orientation of migratory birds (song trushes)

Exposure

- magnetic field
- geomagnetic field

Exposure	Parameters
Exposure 1: unspecified Exposure duration: continuous for 1 h	-

Exposure 1

Main characteristics

Frequency	unspecified
Type	magnetic field
Exposure duration	continuous for 1 h

Exposure setup

Exposure source	coil(s)
Setup	cuboid coil with 1m side length; cage placed in the center of the coil system; magnetic field in this area uniform; magnetic field horizontally rotated; exposure system placed outdoors
Sham exposure	A sham exposure was conducted.
Additional info	for autumn experiments magnetic field deflected 120° clockwise, for spring experiments magnetic field deflected 120° anticlockwise

Parameters

No parameters are specified for this exposure.

Exposed system:

animal
song trush (Turdus philomelos)
whole body

Methods Endpoint/measurement parameters/methodology

orientation of migratory birds (flight direction)

Investigated system:

investigation on living organism

Investigated organ system:

sense organs

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The song thrushes chose a seasonally appropriate migratory direction regardless of whether they had been exposed to the magnetic field prior to release or not, both in autumn and spring. The hypothesis that song thrushes calibrate their magnetic compass from celestial twilight cues is not supported; instead, the hypothesis of the magnetic or stellar compass dominating is confirmed.
The authors suggest that different songbird species possess different hierarchies of orientation cues, depending on the geographic and ecological challenges met by the migrants.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Russian Foundation for Basic Research (RFBR), Russia

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