Predictors and consequences of nest-switching behavior in barn swallows (Hirundo rustica erythrogaster)
Nest switching is an important breeding strategy for multiple brooded bird species that reuse nests. When switching between nests for subsequent clutches, pairs must weigh the costs and benefits of various factors implicated in reproductive success of the first breeding attempt, including total reproductive success, nest predation, the quantity of nest ectoparasites, and the age of the first nest. In this study, I analyzed the predictors and consequences of nest-switching behavior in several populations of North American barn swallows (Hirundo rustica erythrogaster), in Boulder County, Colorado, USA, which often switch nests (60.20% of pairs) for a second clutch. Pairs that reused existing (old) nests were the most likely to switch nests for a second clutch. Additionally, pairs with higher reproductive success in their first nest re-nested closer to their original nest than those pairs that had lower reproductive success. Lastly, the consequences of nest switching were a potential decrease in nest ectoparasites in the second nest, a decrease in the time between clutches, and an increase in reproductive success, but only for pairs that switched from an old nest. Contrary to previous studies, nest predation and nest ectoparasitism had no influence on whether or not pairs switched between nests, or the distance moved between nests. It is possible that pairs switch nests for subsequent clutches to allocate more time to reproduction by utilizing preexisting old nests and overlapping their clutches, and pairs reduce ectoparasites by chance. Because nest switching leads to greater reproductive success for second clutches, these results suggest that switching between nests is an advantageous nesting strategy for barn swallows.