Paternity in the classical polyandrous black coucal (Centropus grillii)--a cuckoo accepting cuckoldry?

In birds, a high degree of paternal care is expected to correlate with a relatively low frequency of extrapair paternity. If females seek extrapair copulations, they may lose fitness because their partners may reduce paternal care. Conversely, a high degree of paternal care might give females extra opportunities to pursue extrapair copulations, whereas their mates are occupied with offspring care. The aim of this study was to investigate paternity in the classically polyandrous African black coucal. In this sex-role reversed species, males intensively invest in offspring care of altricial young. However, the likelihood of extrapair fertilizations through stored sperm or extrapair copulations seems very high because females lay up to 3 clutches for up to 3 males each. Using 9 novel, highly polymorphic microsatellite loci developed for black coucals, we determined paternity of 127 chicks from 35 nests. Of these, 18 chicks (14.2%) from 13 broods (37.1%) were not fathered by the social male. Black coucals thus have the highest average rate of extrapair paternity reported for any classically polyandrous species. Extrapair young were the result from both extrapair copulations with males outside the female's group of social mates and stored sperm from previous mates. We suggest that males were unable to effectively guard their females to prevent extrapair paternity due to 1) the dense habitat they live in and 2) the onset of incubation before clutch completion. Copyright 2009, Oxford University Press.