Relative reproductive success of female moorhens using conditional strategies of brood parasitism and parental care

Abstract

In a population of moorhens (Gallinula chloropus), at least 27% of netting females laid one or more eggs in a neighbor's nest Females laid parasitically under three conditions: 56% of parasitic eggs were from nesting females that preceded laying a dutch in their own nest by a parasitic laying bout, 19% were from females whose nests were depredated before clutch completion and that laid the following egg parasiticaDy, and 25% were from a small number of females without territories, “non-nesting” parasites, that each laid a series of parasitic eggs. Clutch sizes varied greatly between females, but nesting females each laid a consistent clutch size both within and between seasons for a given mate and territory. Nesting females that employed a dual strategy of brood parasitism and parental care produced extra eggs that they laid in the nests of neighbors before laying a dutch in their own nests. Two out of ten females whose dutches I experimentally removed during the laying period were successfully induced to lay their next egg in the nest of a neighbor. Nesting females that laid parasitically selected their hosts opportunistically from among the nests dosest to their territories. An experiment in which parasitic eggs were removed and hosts left to rear only their own young showed that parasites did not choose hosts that were better parents than pairs with contemporary nests that were not parasitized. Females that only laid parasiticaDy within a given season timed their parasitic laying bouts poorly and achieved no reproductive success. Parasitic young rarely fledged, and the mean seasonal reproductive success of nesting brood parasites did not differ from that of nonparasitic females. However, the variance in reproductive success of nesting brood parasites was significantly higher than that of nonparasitic females.