Courtship Feeding and Reproductive Success in Black-Legged Kittiwakes

We assessed the relative importance of the "nutritional hypothesis" and the "copulation enhancement hypothesis" as explanations for the function of courtship feeding in Black-legged Kittiwakes (Rissa tridactyla). The nutritional hypothesis received the most support from our data. In the two weeks prior to egg laying, female kittiwakes at Cape St. Mary's, Newfoundland received approximately 40 food boluses from their mates. As many of these boluses were whole fish, this represents a substantial amount of food. Surprisingly, there were no significant positive correlations between feeding rate and any general measures of breeding success. There may have been sufficient food in 1990 for even inexperienced birds to reproduce successfully, as breeding success was very high that year. The phenology of courtship feeding provided further evidence for the nutritional hypothesis. Courtship feeding rate increased steadily during the period of yolk formation (day -12 to day of egg laying) and reached a peak at day -2, shortly before albumen synthesis, the time of maximum protein demand. Less evidence was found to support the copulation enhancement hypothesis. Although courtship feeding was not essential for successful copulation (60% occurred without prior feeding), if feeding did occur, subsequent copulations were more likely to be successful (end in cloacal contact). However, prior courtship feeding did not result in greater numbers of cloacal contacts per mount and feed size (boluses per feed) had no significant effect on the success of subsequent copulations.