PATERNITY ASSURANCE BEHAVIOR IN THE HOUSE MARTIN DELICHON-URBICA

Sexual behaviour of colonial House Martins was studied to reveal any behavioural strategies of males to protect their paternity. House Martins copulated inside their nests and resident males frequently intruded at their neighbours' nests. Intrusions were frequent, especially during the morning hours of the resident female's fertile period, when intrusions occurred on average every 10 min per nest. A limited data set on copulations indicated a rather low copulation rate, which contrasts with the general pattern for colonial birds. Evidence from the pre-fertile and fertile periods suggested that males tried to minimize the time the female was alone in the nest: males spent approximately 80% of their time in the nest, pair mates spent significantly more time together in the nests than would be expected from a random model, and males did not leave the nest when the female was inside. These observations suggest that staving together with the female in the nest is more important to the male than guarding the nest per se. Hence, male House Martins seem to perform mate guarding restricted to the nest. However, the time budget data are also consistent with the hypothesis that males stay with the female all the time in order to be present when she is ready to copulate. This idea and the mate-guarding hypothesis are not mutually exclusive. but the fact that resident males fought forcefully to evict intruders supports the mate-guarding hypothesis. The selective value of a male mate guarding strategy restricted to the nest is discussed.