Effects of territorial intrusions, courtship feedings and mate fidelity on the copulation behaviour of the osprey

We studied copulation behaviour of the osprey, Pandion haliaetus, a semicolonial, fish-eating raptor, in Corsica (Mediterranean). Pairs copulated over a long period (45 days) and at a high rate, with, on average, 288 within-pair copulations (WPCs) for a clutch. Pairs breeding at higher density faced more frequent territorial intrusions than others and were potentially at an increased cuckoldry risk. However, and contrary to predictions of the ‘paternity assurance’ hypothesis for frequent copulations, we found that WPC rate decreased with increasing frequency of territorial intrusions. Male territory attendance increased with territorial intrusion frequency, to the detriment of the food provisioning of the female. Both attempted and successful WPC rates were positively related to the amount of food delivered by the male. Thus, the more frequent the territorial intrusions, the more time the male spent within his territory, the less he courtship fed and the smaller the fish he delivered, and the less the pair copulated successfully. WPC rate was also higher in newly formed pairs than in established pairs, and decreased with increasing pair bond length. The results suggest that males rely on mate guarding rather than frequent copulations to ensure paternity, and do not support the idea that sperm competition is the main cause of frequent WPCs. Nonfertilization functions of frequent copulations, such as pair bonding, mate assessment and mate retention, were likely early in the prelaying period. The findings that WPC rate decreased with mate fidelity and that females traded copulations for food suggest that mate retention was a possible function of frequent copulations in this species. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.