RELATIVE REPRODUCTIVE SUCCESS OF FEMALE MOORHENS USING CONDITIONAL STRATEGIES OF BROOD PARASITISM AND PARENTAL CARE

In a population of moorhens (Gallinula chloropus), at least 27% of nes ting 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 clutch in their own nest by a p arasitic laying bout, 19% were from females whose nests were depredate d before clutch completion and that laid the following egg parasitical ly, and 25% were from a small number of females without territories, ' 'non-nesting'' parasites, that each laid a series of parasitic eggs. C lutch sizes varied greatly between females, but nesting females each l aid a consistent clutch size both within and between seasons for a giv en mate and territory. Nesting females that employed a dual strategy o f brood parasitism and parental care produced extra eggs that they lai d in the nests of neighbors before laying a clutch in their own nests. Two out Of ten females whose clutches 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 select ed their hosts opportunistically from among the nests closest to their territories. An experiment in which parasitic eggs were removed and h osts left to rear only their own young showed that parasites did not c hoose hosts that were better parents than pairs with contemporary nest s that were not parasitized. Females that only laid parasitically with in a given season timed their parasitic laying bouts poorly and achiev ed no reproductive success. Parasitic young rarely fledged, and the me an seasonal reproductive success of nesting brood parasites did not di ffer from that of nonparasitic females. However, the variance in repro ductive success of nesting brood parasites was significantly higher th an that of nonparasitic females.