Individual effort, social strategies and cognitive skills influence nest-prospecting decisions in brown-headed cowbirds

Abstract

We examined nest-prospecting and egg-laying patterns of female brown-headed cowbirds, Molothrus ater , living and breeding in a large aviary. We tracked every visit every female made to mock host nests throughout their breeding season. Over the course of the breeding season, we experimentally manipulated the number of eggs present in nests. Some of the females had been tested on controlled cognitive tests in the laboratory previously, allowing us to examine how individual cognitive abilities related to their nest selection strategies. We found that females engaged in different patterns of nest visits during prospecting (later in the day) compared to laying (earlier in the day), and that females’ prospecting patterns on one day predicted their egg-laying patterns the next. Also, all females showed strong preferences to prospect and to lay in nests that changed in egg number across days, with females who demonstrated better learning proficiency in cognition tasks being more accurate at laying in changing nests. Cognitive performance was also related to the amount of time females spent prospecting, with better learners investing more time and effort in prospecting nests than less cognitively skilled females. Nest visit patterns clustered in time. Social network analyses revealed that less cognitively skilled females were more likely to follow skilled females to nests during prospecting. Taken together, this experiment provides a new means to examine the individual skills and social skills involved in nest parasitism decision making.