Reproductive success and parental effort of females in polyterritorial wood warblers Phylloscopus sibilatrix: The influence of nest predation

The polygyny threshold model explains that female choice of already-mated males should be selected for when mated males have resources that compensate for the cost associated with sharing the male with another female. We investigated the consequences of mating a mated or an unmated male on female reproductive success and parental effort in polyterritorial wood warblers Phylloscopus sibilatrix, and the influence of nest predation on the amount of male assistance to females of polygynous males. The number of fledged young did not differ significantly between females of different mating status. Females of polygynous males increased their parental effort over the whole nestling period, compensating for reduced male assistance. Mainly because of nest predation suffered by primary females, not all females that mated already-mated males had to share their males with a primary female during the nestling period. Using a more general model on the influence of different amounts of nest predation on parental effort, we also show how different amounts of nest predation influence parental effort of females of polygynous males.