Abstract
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 re-orientation), 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.
Highlights
The ability of migratory birds to perform their spectacular long-distance journeys and yet precisely locate their breeding or winter grounds has fascinated both scientists and general audiences alike
Displacement experiments have provided strong evidence that birds translocated from their migratory route perform true navigation (Mouritsen 2018)
We focused on the role of the sense of smell for longdistance navigation in a migratory songbird species—the Eurasian Reed Warbler (Acrocephalus scirpaceus; hereafter Reed Warblers)
Summary
The ability of migratory birds to perform their spectacular long-distance journeys and yet precisely locate their breeding or winter grounds has fascinated both scientists and general audiences alike. Displacement experiments have provided strong evidence that birds translocated from their migratory route perform true navigation (Mouritsen 2018). This means that they are capable of identifying and reaching their goal, without direct sensory contact with it, from a place they have never previously visited (e.g., Perdeck 1958; Thorup et al 2007; Chernetsov et al 2008; Willemoes et al 2015; but see Kishkinev et al 2016). The ability of an animal to determine its current geographic position relative to the goal (a map sense) is crucial. We focused on the role of the sense of smell (olfactory system) for longdistance navigation in a migratory songbird species—the Eurasian Reed Warbler (Acrocephalus scirpaceus; hereafter Reed Warblers)
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