Polygyny in the pied flycatcher,Ficedula hypoleuca: a test of the deception hypothesis

The deception hypothesis has been proposed as an explanation for polygyny in the pied flycatcher. According to this hypothesis, already-mated males hide their mating status with polyterritorial behaviour and thereby increase their chances of obtaining a second mate. In a study area at Oslo, Norway, secondary females raised 84% as many fledglings as did concurrent monogamous and primary females. The unmated males sang most of the time near their nest site, whereas the already-mated males frequently disrupted singing for longer periods in their secondary territories to visit their primary nest; such visits to the primary nest occurred both before and after the time of their second mating. The behaviour of the males suggests that deception of females is not an evolutionarily stable strategy, as an observant female would soon discern the male's status. Another difficulty with the deception hypothesis is that secondary females laid larger clutches than primary females. The number of young fledged from secondary nests was not dependent on the distance to the primary nest. The deception hypothesis was not supported by the data, and the reduced reproductive success of secondary females may be explained by the cost of searching for a mate.