COURTSHIP FEEDING AND REPRODUCTIVE SUCCESS IN BLACK-LEGGED KITTIWAKES

We assessed the relative importance of the ''nutritional hypothesis'' and the ''copulation enhance ment hypothesis'' as explanations for the function of courtship feeding in Black-legged Kittiwakes (Rissa trida ctyla). 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 t heir mates. As many of these boluses were whole fish, this represents a substantial amount of food. Surprisingly there were no significant p ositive correlations between feeding rate and any general measures of breeding success. There may hare 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 furt her evidence for the nutritional hypothesis. Courtship feeding rate in creased steadily during the period of yolk formation (day -12 to day o f egg laying) and reached a peak at day-2, shortly before albumen synt hesis, the time of maximum protein demand. Less evidence was found to support the copulation enhancement hypothesis. Although courtship feed ing was not essential for successful copulation (60% occurred without prior feeding), if feeding did occur, subsequent copulations were more likely to be successful tend in cloacal contact). However, prior cour tship feeding did not result in greater numbers of cloacal contacts pe r mount and feed size (boluses per feed) had no significant effect on the success of subsequent copulations.