Parental care and sociality in a communally breeding bird, the greater ani

Abstract

Parental care confers important fitness benefits in a variety of taxa, but it also can pose challenges. When more than one individual contributes to parental care, caregivers must cooperate and coordinate with each other to reach a shared goal. In cooperative breeders, in which more than two individuals contribute to offspring care, these challenges are more complex than in species with biparental care. Understanding the evolution and maintenance of parental care in these cooperative systems requires investigating how individuals might vary in their contributions to care and interact with other group members with which they share caregiving responsibilities. My dissertation explores these topics in a communally nesting bird, the greater ani (Crotophaga major), in which two or three unrelated mated pairs raise their young in a single nest. I conducted behavioral observations on a breeding population of greater anis in central Panama and leveraged a long-term data set on the same population to investigate parental care and group dynamics. In Chapter 1, I review the literature on individual variation in contributions to cooperative tasks, both in terms of overall workload and specializations on specific tasks (division of labor), and explain how combining these two approaches can yield a more complete understanding of cooperation across contexts. In Chapter 2, I use the framework from Chapter 1 to investigate whether greater ani breeding groups exhibit unequal parental care workload distribution or division of labor. In Chapter 3, I test whether ani group members synchronize their visits to the nest and whether such synchrony impacts fitness. In Chapter 4, I investigate whether changes in group composition influence the likelihood of reproducing in a given year. Overall, my work on parental care contributions and interactions among breeding group members contributes to our understanding of various details of parental care and cooperative breeding that have often been overlooked despite their potential fitness consequences.