Determinants of nest box local recruitment and natal dispersal in a declining bird population

Recruitment and dispersal are important demographic rates and studying their determinants is particularly important in the current context of global anthropogenic perturbations. In birds, and especially for migratory species, assessing these rates is challenging because of the difficulties involved in tracking individuals beyond fledging. Here we assessed the determinants of nest box local recruitment and natal dispersal distances in a declining aerial insectivore, the Tree swallow (Tachycineta bicolor). We used a 16-year dataset obtained from the long-term monitoring of a population breeding within a 10,200-km2 study system located along a gradient of agricultural intensification in southern Québec, Canada. Yearly nest box local recruitment rates ranged there in between 1.0% and 3.2%. Heavier nestlings who fledged earlier were more likely to recruit. Natal dispersal distances were generally short (mean ± SD = 12.7 ± 13.8 km) in the study system and were influenced by different factors ...