The frequency and function of aquatic courtship and copulation in Least, Crested, Whiskered, and Parakeet Auklets

Least (Aethia pusilla), Crested (A. cristatella), Whiskered (A. pygmaea), a nd Parakeet Auklets (Cyclorrhynchus psittacula) all engage in aquatic court ship and copulation behavior. We quantified auklet sexual behavior at sea t o obtain comparative information related to sexual selection and to evaluat e why auklets choose this unusual location for mating. Auklet courtship inv olved a variety of stereotyped displays. Although similar courtship display s occurred both at the colony on land and at sea, copulation took place onl y on the sea. Courtship and copulation was frequently disrupted by extrapai r males. Extrapair copulation attempts occurred in all species and apparent ly successful unforced extrapair copulations were observed in Least, Creste d, and Whiskered Auklets, suggesting that sperm competition is a feature of their mating systems. Male birds risk water damage to their sperm if they mount their female partners at sea and cause their cloacas to become submer ged during insemination. Male auklets, lacking an intromittent organ, achie ved cloacal contact without mounting the female so that their cloacas remai ned unsubmerged. Males positioned themselves behind their partners and rapi dly flapped their wings, creating lift to bring their cloacas up against th eir partner's cloacas, pushing upwards and ensuring insemination occurred a way from the sea surface. Possible hypotheses to account for exclusively aq uatic copulation include predation and sexual harassment avoidance, and fem ale testing of males, but a definitive explanation for this phenomenon rema ins elusive.