HIGH-FREQUENCY OF CUCKOLDRY IN PIED AND COLLARED FLYCATCHERS

Tarsus lengths of fully grown nestlings of pied and collared flycatchers resembled more the female than the male associated with the nest. The lower slope of the male-offspring regression in the flycatchers is ascribed to a high frequency (24%) of multiple paternity within broods. The most likely cuckolder was the nearest neighbor male since tarsus length of neighbor males correlated positively with that of the young. The high frequency of cuckoldry among flycatchers is probably due to the polyterritorial behavior of males.