It's not all about chimneys: Informing conservation of the natural nesting habitat of Chaetura pelagica (Chimney Swift)

Chaetura pelagica (Chimney Swift), a threatened aerial insectivore in Canada, has experienced a reduction in its natural nesting and roosting habitat following European settlement in North America. The species quickly adapted to masonry chimneys and is now considered to nest primarily in urban environments. Due to a lack of knowledge regarding the characteristics of natural nesting habitat, critical natural habitat could not be defined in the Canadian recovery strategy. In this study, we characterized the natural nesting habitat of C. pelagica at multiple spatial scales. Between 2019 and 2024, we radio-tagged 114 C. pelagica and located 22 nesting trees. The relative tree selection probabilities increased with tree diameter and decay. Several cavity types were used by C. pelagica, with selection probability increasing with cavity diameter; chimney trunk rot-holes were preferred. Nesting trees were more frequently found in old forest stands with a high density of large-diameter deciduous trees (>70 cm). At the landscape scale, the relative selection probabilities of nesting tree were positively influenced by the proportion of old deciduous forest up to 2 km. These findings represent an important step toward informing conservation efforts and the recovery plan objective for a long-term transition from chimneys back to natural habitats.