Olfactory discrimination of plant volatiles by the European starling

Passerine species that re-use nest sites often incorporate fresh green vegetation into their nests, a behaviour consistent with the possibility that some birds may use chemical properties of plants to counteract the selective potential of parasites and pathogens. We tested adult starlings (Sturnus vulgaris) for their physiological capacity and behavioural ability to detect and discriminate between volatiles emitted from plant material. Multi-unit electrophysiological recordings from olfactory nerves of adults indicated that strong responses were reliably elicited by volatiles from six plant species. After pairings of plant volatiles with gastro-intestinal malaise, birds exhibited conditioned avoidance in behavioural experiments, and made all possible pairwise discriminations between volatiles of the various plant species. Bilateral olfactory nerve cuts prior to conditioning abolished the ability to acquire avoidance, suggesting that olfactory cues mediated the response to plant species. These and previous results suggest that starlings use volatile cues to discriminate and choose between plants used in nest construction.