Bird-Scented Nests as a Mechanism for Olfactory Homing in a Burrow-Nesting Seabird.

AbstractNavigation to and from a familiar site is a common animal behavior called homing. Many species use olfactory environmental landmarks or scents deposited in the environment by themselves or their conspecifics for homing. Birds regularly commute to and from their nest, and olfaction, an underappreciated sense in birds, may facilitate this behavior. Burrow-nesting seabirds, for example, rely on olfaction to locate their breeding colony and to identify their burrow, but the specific chemical information they use is unclear. We examined the chemical profiles of the colony landscape and its avian occupants at a breeding island of Leach's storm petrels (Hydrobates leucorhous) to determine whether place-specific chemicals, bird-produced chemicals, or both enable homeward navigation in this burrow-nesting species. We found that the colony contains spatial gradients of chemicals that may facilitate multiple stages of homing. We also show that burrows possess unique odors owing to chemicals deposited by their occupants. Moreover, the burrow shapes the odor of the birds such that individuals carry the scent of their nest and mated pairs possess similar chemical profiles. The bidirectional transfer of compounds between burrows and birds may enable burrow recognition in this species and potentially functions as a means of communication between conspecifics.