MATE/SITE FIDELITY: Exhibits mate and site fidelity, and normally mates for life (Dexter 1951b, Dexter 1992). In Ohio, 84.5% of nesting swifts under observation retained the same mate when both returned for nesting, and 96% of the pairs that returned and nested together occupied the same air shaft used in the previous year (Dexter 1992). In New York, two pairs mated for three successive summers and five pairs mated for two successive summers (Fischer 1958). Sixty-two percent of banded adults returned to the New York study area and of these 70.5% returned to their previous nest site (Fischer 1958). In Kingston, Ontario, 9.7% of banded bird returned to the study area (Bowman 1952). One bird, banded at Rome, Georgia was subsequently captured at Kent, Ohio, then captured again at Rome (Dexter 1979). In New York, 11% of birds banded as nestlings returned to the study area, and 70% of these returned to their natal site to breed (Fischer 1958).
WEATHER: The time interval between visits to feed young increases at temperatures above or below 21-24 C, and on windy or rainy days (Zammuto et al. 1981). Most individuals leave the roost during light levels of 0-0.65 lux, and return to roost at light levels of 0-0.19 lux (Zammuto and Franks 1981). On cold, rainy mornings, emergence from the roost is either delayed or birds soon return after leaving. On windy days, birds leave the roost earlier and return later than on calm days (Zammuto and Franks 1981). Relatively cold or warm temperatures, wind, and rain all reduce flying insect abundance and apparently decrease swift foraging efficiency (Zammuto and Franks 1981, Zammuto et al. 1981).
POPULATION PARAMETERS: At Kingston, 177 banded swifts were still alive six years after banding (Bowman 1952). Annual mortality is estimated to be 50% (Fischer 1958). Lives to be 14 years old (Terres 1991).