The Cliff Swallow (Petrochelidon pyrrhonota) is a highly colonial species that occurs throughout much of North America (Brown et al. 2020). Historically, it nested on vertical cliffs in the western mountains, but expanded east as it adapted to man-made structures such as bridges and buildings. Although the species’ population is generally increasing (Sauer et al. 2017), there is considerable regional variation, with significant declines in the western and northern portions of its range. In New Hampshire, there were over 80 colonies during the Breeding Bird Atlas in 1980-85 (Foss 1994), but more recent surveys have only documented 20-25 colonies supporting roughly 150 breeding pairs (Hunt 2018). Because of this decline the species was listed as State Threatened in 2017.
Program Report: 2023 NH Audubon Cliff Swallow Grant Report August