Comments: Cosmopolitan; inhabits rural and urban environments having both an abundance of flying arthropods and suitable roosting/nesting sites. Nests principally in chimneys, but also on the interior walls of a variety of other anthropogenic structures including silos, barns, outhouses, uninhabited houses, boathouses, wells, and cisterns (Bent 1940). Natural nest sites include the interior of hollow tree trunks and branches, Pileated Woodpecker cavities and rock shelters (Bent 1940, Fisher 1958, Hofslund 1958). Trees in which nests have been found include American Beech (Fagus grandifolia), Yellow Birch (Betula lutea), Silver Maple (Acer saccharinum), Sycamore (Platanus occidentalis), Bald Cypress (Taxodium distichum), and Water Nyssa aquatica; Blodgett and Zammuto 1979, Fischer 1958, Hofslund 1958, Mumford and Keller 1984, Stevenson and Anderson 1994). Due to the prevalence of nesting structures in areas populated by humans, often occurs at higher densities in anthropogenic environments than natural ones (i.e., forests; Beissinger and Osborne 1982). Migrating flocks roost overnight principally in chimneys, but also in hollow trees or, rarely, even exposed on tree trunks (Bent 1940, Spendelow 1985).