Dusky Warbler (Phylloscopus fuscatus) Science Article 1
The polygyny threshold model states that secondary females gain benefits from high territory quality thatoutweigh the costs of sharing a male. We aimed to test this prediction using the dusky warbler as a modelspecies. We first showed that neither the shifted sex ratio hypothesis nor the no-cost models were likelyto apply to our study. Secondary females settled in territories of higher quality (high food abundance, lowpredator density) and had a nonsignificantly higher reproductive success than simultaneously settlingmonogamous females. However, there were strong indications that these two groups of females differedintrinsically. Secondary females were older than late monogamous females, and while they replaced lostclutches more often, they also suffered from a nonsignificantly higher winter mortality. Consequently, itwas impossible to tell whether differences in reproductive success were caused by differences in territoryquality or in female qualities. Our study suggests that female choice may also depend on characteristicsthat are specific to the individual, and may therefore be more sophisticated than allowed for in traditionalpolygyny models. In other words, the polygyny threshold may be not the same for all individuals. Wesuggest that prior breeding experience may help older females to profit more from the benefits and tosuffer less from the costs of polygyny than young females.
Wolfgang Forstmeier, Dries P. J. Kuijper & Bernd Leisler, ANIMAL BEHAVIOUR, 2001, 62, 1097-1108