Odor is linked to adrenocortical function and male ornament size in a colonial seabird

Crested auklets (Aethia cristatella), colonial seabirds of Alaska and Siberia, emit a citrus-like odorant from wick-like feathers. We examined whether the odorant emission is linked to adrenocortical function and correlated with size of the crest feather ornament. Conventional signals like the size of crest ornament are inexpensive to produce and thus may be prone to deception. However, assessment signals such as the odorant could be more reliable if they impose costs and more proximate since they are continually produced. This may be the case for the crested auklet’s volatile aldehyde odorant. The signal is composed of highly volatile chemicals that appear to be products of fatty acid metabolism. Adrenocortical function helps to mobilize endogenous resources for metabolism. Elevation of corticosterone may be needed to sustain a reliable chemical signal, but there are physiological costs for prolonged elevation of circulating corticosterone. We predicted that higher odorant em...