The fork-tailed swift is generally considered to be a migratory species, although not all of the subspecies necessarily migrate. Apus pacificus pacificus is a long-distance migrant, wintering in Indonesia and Australia between October and April, whereas the other three more southerly subspecies tend to be mainly resident, or only migrate short distances (2).
A gregarious species, the fork-tailed swift is generally found in large flocks (2), often mixing with other species of swift (6) (11). However, when foraging it is most commonly found in small groups of three to five birds (2). An aerial feeder (8) (9), the fork-tailed swift never voluntarily settles on the ground (9), and catches its insect prey while in flight (2) (9).
The type of prey taken varies with the location, but flies, termites and bees are among the insects recorded as part of the fork-tailed swift’s diet (2). The fork-tailed swift flies very fast as it forages (8), and it is known to make erratic flutters and turns when feeding (6), often being highly vocal (3).
The timing of the fork-tailed swift’s breeding season varies depending on location, occurring between March and May in Nepal, April to June in the Himalayas, and between June and August in Japan (2).
The fork-tailed swift’s nest is a half-cup made of vegetable matter which is stuck together using saliva (2). Saliva is also used to fix the nest to the sloping face of a cliff fissure or under the roof of a building (2) (3). The female fork-tailed swift lays a clutch of between one and three eggs, and both adults take part in all nest duties. The eggs are incubated for a period of 17 days, and the chicks fledge at about 40 days old (2). The fork-tailed swift returns to the same nest site year on year, simply rebuilding the nest when necessary (9).