Behaviour 2019
Mated pairs of swallows with similar personality types share nestling care evenly and achieve higher fitness
Tyler J. Pyle1, Kristen R. Content1,2, Lynn Siefferman1. 1Department of Biology, Appalachian State University, Boone, North Carolina, United States; 2Department of Biology, Indiana University, Bloomington, Indiana, United States

There has been some evidence that mated pairs with similar personality types have increased fitness, but little research has focused on potential mechanisms behind this pattern. We tested the hypothesis that pairs with similar personalities better enables coordination in parental care behaviors and leads to increased offspring growth. We studied breeding tree swallows (Tachycineta bicolor), a highly aggressive species with bi-parental care. Past research demonstrates that individual swallows display repeatable consistent aggressive phenotypes (personality). We measured nest defense aggression in response to a predator simulation and found that the aggression within birds was repeatable, and breeding pairs behaved similarly. Moreover, mated pairs with similar aggressive phenotypes contributed more equally to offspring provisioning, had higher levels of alternations, were more synchronous in their nest visits, and produced larger, faster growing offspring. These data suggest that the benefits of pairs with similar personalities in species with bi-parental care may be a consequence of better coordination of parental care duties and shed light on the evolution of parental conflict.