Evidence that blue petrel, Halobaena caerulea, fledglings can detect and orient to dimethyl sulfide

Procellariiform seabirds (the petrels, albatrosses and shearwaters) are recognized for their acute sense of smell. These pelagic seabirds forage over thousands of miles of ocean to find patchily distributed prey resources. Over the past decade, much headway has been made in unravelling the variety of olfactory foraging strategies that Antarctic species employ, and it is becoming clearer that olfaction plays a key role in foraging, particularly for burrow nesting species. Now we are beginning to explore how these behaviours develop in chicks. Procellariiform chicks fledge and survive the open seas without aid or instruction from a parent, but how they are able to accomplish this task is unknown. Here we explore whether chicks leave the nest pre-tuned to olfactory cues necessary for foraging. In this study, we tested the hypothesis that blue petrel chicks (Halobaena caerulea) are able to detect and orient to a foraging cue (dimethyl sulphide, DMS) used by adults without ever having experienced this odour at sea. We first established that chicks could detect DMS at a biologically relevant concentration that they will later naturally encounter at sea (<10 pmol l-1). We then performed preference tests in a Y-maze on a group of birds 1-6 days before they fledged. Sixteen out of 20 fledglings preferred DMS (e.g. DMS+propylene glycol) to a ;control' odour (propylene glycol alone). Our results suggest that chicks can detect and may already recognize DMS as an orientation cue even before they leave the nest to forage for the first time.