CONSPECIFIC BROOD PARASITISM AS A FLEXIBLE FEMALE REPRODUCTIVE TACTIC IN AMERICAN COOTS

Conspecific brood parasitism was a common component of reproduction in a population of American coots, Fulica americana, in central British Columbia, Canada. In a 4-year study, over 40% of nests were parasitized and 13% of all eggs were laid parasitically. Parasitism occurred in several ecological contexts, each involving different constraints and trade-offs. A quarter of the parasitic eggs were attributed to floater females without nests or territories of their own. The annual reproductive success of floaters was 16 times lower than that of territorial, nesting females, indicating that parasitism was a low-paying alternative to non-breeding rather than a specialized, equal-fitness alternative to nesting. Nest loss during laying accounted for few cases of parasitism. Most of the parasitism in the population was attributed to nesting females that laid additional eggs parasitically. One quarter of the nesting females were parasitic, and these females usually laid parasitically prior to laying full-sized clutches in their own nests. Brood reduction through starvation was prevalent in all years and on all wetlands, indicating that post-hatching parental care limits the number of offspring that pairs can raise in their own nests. By laying surplus eggs parasitically, females can bypass the constraints of parental care and increase their total production of offspring. As a flexible reproductive tactic used in several ecological contexts, parasitism permits a more finely tuned life-history strategy for dealing with reproductive and social constraints. Copyright © 1993 The Association for the Study of Animal Behaviour.