Star compass learning: how long does it take? (original) (raw)

Abstract

Young night-migratory birds establish a functional star compass during ontogeny by searching the starry night sky for its centre of rotation and interpreting this as “north”. The birds then use the learned location of the rotational centre to calibrate their magnetic compass. Here, we examine the required duration of this learning process. We exposed three groups of hand-raised inexperienced European Robins Erithacus rubecula to a rotating artificial star pattern for 3 weeks, 1 week, or 1 night, respectively, during ontogeny. A control group was exposed to the same, but stationary, artificial star pattern for 3 weeks. During their first autumn migration, we tested the birds’ orientation under the stationary star pattern as well as in the local geomagnetic field with no stars visible. Only the group that had the longest exposure time to celestial rotation during ontogeny was able to show orientation in the appropriate direction during autumn migration in the local geomagnetic field in relation to the memorized former centre of celestial rotation. This suggests that these birds had calibrated their magnetic compass relative to the star pattern seen during ontogeny. All other groups showed inappropriate or random orientation both under the stationary star sky and in the local geomagnetic field, suggesting that 7 nights of observing celestial rotation are not sufficient for young European Robins to establish a star compass and to calibrate their magnetic compass accordingly.

Zusammenfassung

Das Erlernen des Sternenkompasses: Wie lange brauchen Zugvögel dafür?

Junge, nachts ziehende Singvögel entwickeln einen Sternenkompass während ihrer Ontogenie, indem sie den nächtlichen Sternenhimmel beobachten, das Rotationszentrum ermitteln und dieses für sich als “Norden” interpretieren. Anschließend wird mit Hilfe dieses Wissens über die Lage des Sternen- Nordens ihr magnetischer Kompass kalibriert. In der vorliegenden Studie untersuchen wir, wie lange Vögel für diesen Lernprozess benötigen. Wir bildeten drei Gruppen von jungen, unerfahrenen, handaufgezogenen Rotkehlchen Erithacus rubecula und präsentierten ihnen für jeweils drei Wochen, eine Woche bzw. nur eine Nacht ein künstliches, rotierendes Sternenmuster. Während ihres ersten Herbstzuges testeten wir die Vögel sowohl unter dem stationären Sternenmuster als auch im lokalen Erdmagnetfeld ohne sichtbares Sternenmuster. Lediglich die Gruppe, die während der Ontogenie am längsten den rotierenden Sternenhimmel beobachten durfte, konnte eine entsprechende Orientierung im lokalen Erdmagnetfeld bezüglich des erinnerten Rotationsfixpunktes zeigen. Dies legt nahe, dass diese Vögel während ihrer Ontogenie ihren Magnetkompass bezüglich des Sternenmusters kalibriert haben. Alle anderen Gruppen zeigten weder unter dem Sternenmuster noch im lokalen Erdmagnetfeld eine angemessene Zugrichtung. Das deutet darauf hin, dass sieben Nächte Beobachtung des rotierenden Sternenhimmels während der Ontogenie nicht ausreichen den Sternenkompass zu lernen und den Magnetkompass entsprechend zu kalibrieren.

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Acknowledgments

We thank Thomas Geiger and co-workers of the electronic and mechanical workshops of the University of Oldenburg for constructing the star test chambers and Dr. Nils-Lasse Schneider for technical support. We also thank Prof. Dr. Franz Bairlein for his generous support in allowing us to use the excellent facilities of the Institute of Avian Research, Wilhelmshaven, Germany, Kane Brides for assistance to find nests, and Andreas Lischke who provided essential help with hand-raising birds. We thank Inka Spiller, Maike Gärtner, Laura Ziegenbalg and Hanna Seekamp for help with conducting the experiments. Financial funding was provided by the German Federal Ministry of Education and Research (BMBF; “Varying Tunes”, 01 GQ 0962 to H.M.), the DFG (MO 1408/1-2 to H.M.), and the Volkswagenstiftung (Lichtenberg Professur to H.M.).

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Authors and Affiliations

  1. Institut für Biologie und Umweltwissenschaften, University of Oldenburg, 26111, Oldenburg, Germany
    Andreas Michalik, Bianca Alert, Svenja Engels, Nele Lefeldt & Henrik Mouritsen
  2. Research Centre for Neurosensory Sciences, University of Oldenburg, Carl-von-Ossietzky-Straße 9-11, 26129, Oldenburg, Germany
    Andreas Michalik, Bianca Alert, Svenja Engels, Nele Lefeldt & Henrik Mouritsen

Authors

  1. Andreas Michalik
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  2. Bianca Alert
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  3. Svenja Engels
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  4. Nele Lefeldt
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  5. Henrik Mouritsen
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Corresponding authors

Correspondence toAndreas Michalik or Henrik Mouritsen.

Additional information

Communicated by N. Chernetsov.

A. Michalik and B. Alert contributed equally to this paper.

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Michalik, A., Alert, B., Engels, S. et al. Star compass learning: how long does it take?.J Ornithol 155, 225–234 (2014). https://doi.org/10.1007/s10336-013-1004-x

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