Forced extra-pair copulation and mate guarding in the white-cheeked pintail: timing and trade-offs in an asynchronously breeding duck

Abstract

Abstract. Males employing a mixed reproductive strategy may increase their fitness through extra-pair copulations (EPCs), but also risk lost paternity when they leave their own mate unguarded. How males maximize the effectiveness of forced extra-pair copulation (FEPC) attempts while minimizing the risk of cuckoldry was studied in a non-migratory population of the white-cheeked pintail, Anas bahamensis bahamensis, a tropical species with extended breeding seasons. Despite substantial asynchrony in the laying dates of females, males directed FEPC attempts primarily at females in fertile condition. The rate of pair copulations also peaked during the female's fertile period, but 23.1% of all successful copulations with laying females were FEPCs. Males guarded their paternity by vigorously defending their mates from males attempting FEPC, by escorting females to their nests, by defending a territory, and by forcing copulation on their own mates after they had been subjected to an FEPC attempt by another male. Contrary to expectation, males did not temporally partition mate guarding and FEPC activity but pursued FEPCs primarily during the period when their own mates were fertile. There was no evidence, however, of a trade-off between FEPC activity and the quality of male mate guarding. Females paired to males with the highest FEPC rates were rarely subjected to FEPCs themselves. In addition, although females that abandoned nesting efforts suffered a high frequency of FEPC attempts, their mates were much less active in FEPCs than the mates of females that nested successfully. These results suggest substantial variation in male quality: some males excelled at both guarding their mates and achieving FEPCs, while others neither pursued FEPCs nor mate-guarded effectively.