Adaptive nest site choice by birds

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Early in the imperative of reproduction, birds must decide where to breed, taking into account aspects of habitat such as proximity of foraging areas, predators, and vegetative cover. Because nest habitat can have profound influences on reproductive success, there is intense interest in unravelling bases for these decisions. Birds suffering nest failure are presumed to learn and disperse adaptively to better nest habitats. Nest failure is more often ascribed to predation than to any other cause. Accordingly, parents are predicted to invest significantly in strategies to conceal nests from predators. My research program will make novel contributions in rigorously testing aspects of the preceding framework, focusing on evaluating adaptive choices of nest habitat relative to previous nest success, and on parents’ anti-predator defences. I will also mine my 15-year data set on reproduction in tree swallows wherein I have manipulated nest habitat to enable me to test experimentally for effects of nest habitat on reproductive success. Using recapture data, I will test whether adults adaptively choose better nest sites in successive reproductive attempts. Next, I will evaluate strategies of behavioral crypsis; breeding pairs of birds can improve crypsis of nest sites by synchronizing nest visits to limit opportunities for predators to observe feedings. In addition, predators may be more likely to home in on nest locations if parent birds’ approach and departure vectors clearly end at a particular location. Thus, parents that approach nests should depart in a direction that differs by 180 degrees; in this way, a predator may conclude that a bird merely stopped temporarily en route to a final destination. I propose and develop the Choreography Hypothesis that predicts both feeding synchrony and coordinated approach/departure vectors of parents to reduce detection of breeding sites by predators. The hypothesis makes a wealth of original predictions with respect to, for example, predator communities, frequency of feeding, brood value, and how long parent birds have bred together, and influences of the preceding on choreography. Initial testing of the Choreography Hypothesis will be done using tree swallows; subsequent tests will be extended to other species. My research will have broad interest for others working on these critical aspects of Darwinian fitness; my unique and exciting predictions can be tested in a variety of systems. My primary research objectives are to conduct cutting edge research on factors that constitute significant contributors to avian reproductive success and survival. Funding from Canadians through the federal government enables me to train students, one of the most rewarding parts of my research program. My students leave as mature scientists who have unravelled novel aspects of birds’ biology that can have important positive conservation impacts.