From individuals to populations: The direct and indirect effects of predation on waterfowl nest success

Nest predation is the most important factor influencing avian nest success; however, the full impact of predation on nests is poorly understood because few ecologists have approached the processes affecting nest success from multiple scales. Here, I apply a multi-level approach to understanding waterfowl nest success by focusing on predator-prey interactions that occur at multiple levels of organization.; My dissertation begins at the individual level by exploring behavioral decisions that influence waterfowl nest success. I first evaluate the prevalence of partial clutch depredation and show that partially depredated nests contribute substantially to duckling production. Thus, the parental investment decision to desert a partially reduced clutch has important population consequences. Second, I examine nest desertion in response to partial clutch depredation to determine which cues females use to adjust parental care. I show that females are more likely to provide care for proportionately larger clutches, older clutches, and nests with eggs missing rather than with eggshell remains. Thus, several factors influence clutch value and waterfowl use multiple cues to adjust parental care. Third, I experimentally manipulated clutches to test whether females invest according to their past investment or expected benefit from a current clutch. My results suggest that increased parental investment with incubation stage is due to the increasing expected benefits accrued as a clutch ages rather than to a parent's past investment.; Fourth, I focus at the population level and examine whether predation on nests is density-dependent. I experimentally deployed artificial nests at three densities and used natural nests in a companion study to test for density and nearest-neighbor effects on nest predation. I found little support for density-dependent predation.; Finally, I focus at the community level and investigate the predator-mediated indirect effects of coexisting prey on waterfowl nest success. I found that nest success was positively correlated with rodent abundance among sites in all three years and with vole abundance among years. Hence, rodents may buffer predation on nests, both within and among years, via the behavioral responses of shared predators to coexisting prey. Together, my studies illustrate the value of considering nest predation from multiple levels of organization.