A number of studies have shown that migrating birds can navigate to their destinations even when displaced to unfamiliar territory. It has been demonstrated that adult Eurasian Reed Warblers (Acrocephalus scirpaceus) captured in spring in the Eastern Baltic, displaced 1000 km eastward to the Moscow region and tested in orientation cages, show a clear orientation tendency towards their breeding grounds. This response requires the ability to determine a new geographic position relative to the goal. The natural cues that are used as coordinates for this behaviour remain controversial. Among other natural cues, both magnetic and olfactory sources of information have received the most experimental attention. More recently, virtual displacement experiments have shown that the geomagnetic information alone is sufficient for Reed Warblers to find their geographic position. However, the role of olfaction was not explicitly examined. In the present study, we displaced anosmic Reed Warblers together with untreated controls between the same capture and displacement sites where the Emlen funnel tests were previously performed. Following release, we radio-tracked birds for the first few kilometres using an array of automated radio-tracking towers. The results strongly suggest a navigational response of both anosmic and intact birds (anticlockwise reorientation), unlike some other experiments showing impaired navigational abilities of anosmic migrating birds. This data supports the hypothesis that, at least in this songbird species, the olfactory system is not crucial for determining geographic position, and that the zinc sulfate anosmia treatment is unlikely to have any non-specific effects on navigational abilities. Keywords Bird navigation • Eurasian Reed Warblers • Olfactory map hypothesis • Anosmia • Zinc sulfate • Automated radio-tracking • Radio telemetry Zusammenfassung Anosmische Singvögel kompensieren ihre Zugrichtung nach geografischer Versetzung: eine "radio-tracking" Studie. In vielen Studien ist gezeigt, dass Zugvögel in der Lage sind, auch nach geografischer Versetzung in vorher unbekannte Gebiete zu ihren Brutgebieten zu navigieren. So kompensierten im Frühjahr im Kaliningrad-Gebiet gefangene Teichrohrsänger (Acrocephalus scirpaceus), die etwa 1000 Kilometer ostwärts in die Region um Moskau verbracht und nachfolgend in Emlen-Trichtern getestet wurden, für diese Versetzung und zeigten Orientierungsverhalten mit klarer Tendenz zu den nun nordwestlich gelegenen Brutgebieten. Dieses Verhalten impliziert einen Mechanismus, der diese geografische Versetzung Communicated by H. Mouritsen.

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Much evidence suggests that some passerines during seasonal migrations can perform regional-scale movements, both in the migratory and in the reverse direction. The scale of such movements exceeds the scale of typical stopover movements, but is usually smaller than most migratory flights. We studied regional-scale movements during autumn migration in short-distance migrants of three passerine species: European Robin (Erithacus rubecula Linnaeus, 1758), Goldcrest (Regulus regulus Linnaeus, 1758), and Long-tailed Tit (Aegithalos caudatus Linnaeus, 1758), by analyzing ringing and recapture data from 7 sites on the southeastern Baltic coast at a distance of 11–132 km from each other. The number of birds involved in regional movements varied significantly between species. Long-tailed Tits migrate during the day, and the proportion of birds performing regional-scale movements was one to two orders of magnitude higher than in European Robins (nocturnal migrants) or Goldcrests (migrants with a mixed migratory rhythm). In all three species, the average dates of their regional-scale movements over short distances did not differ significantly between individuals that moved in the migratory and the reverse direction. Regional-scale movements often occurred under headwinds, which suggests that these movements could be caused by aborting migratory flights and (or) by drifting in such winds.