Résumé
Procellariiform seabirds (petrels, albatrosses and shearwaters) navigate vast distances over seemingly featureless ocean habitat by mechanisms that are not well understood. These birds have large olfactory bulbs, and the use of smell has been implicated in both foraging and homing behavior. While many olfactory cues relevant to these behaviors have been identified, ammonia is a potentially significant, biogenic, scented compound that has not been studied in this context. Ammonium (NH₄⁺) constitutes a primary waste product produced by many of the prey species on which procellariiforms forage. Nitrogen waste products, including volatilized ammonia (NH₃), also scent the terrestrial landscape of sub-Antarctic islands where newly breeding procellariiform seabirds recruit and raise their young. Since an ability to smell ammonia may be relevant to both prey detection and locating colonies or islands, we used a non-invasive, behavioral assay to examine whether this scented compound is detectable by a candidate test species, the blue petrelHalobaena caeruleaGmelin. Our results suggest that these birds can detect volatilized ammonia within a concentration range that they may naturally encounter (10–11to 10–5M), and point to ammonia as a potential signal molecule in the sub-Antarctic.