Locomotion is generally via flight, though swifts have been observed climbing the walls of nest and roost caves (Whitacre 1989).
The flight is "deceptively fast and powerful with deep, steady, and fluid wing beats" (Hilty 2003). The White-collared Swift had "the highest flapping and gliding flight velocities" of five species of large swifts studied in Costa Rica (Marín and Stiles 1992). These authors further describe the flight of White-collared Swift as very rapid but buoyant, "ascending, descending and circling with virtually no flapping;" indeed, "the only time one regularly sees S. zonaris give a rapid series of flaps on extended wings is when a bird slows ... to catch an insect before accelerating again." The flight speed may exceed 70-100 kph (Marín and Stiles 1992).
Little information. Marín and Stiles (1992) described what they believed to be courtship chases, involving small groups of 2-4 individuals. One bird (the presumed female) led the chase, pursued to the other individual(s). The chases were accompanied by loud screeches, and "involved much twisting and turning in unison at high speed with the birds often practically touching in the air."
Marín and Stiles (1992) also observed apparent aerial copulations.
Social and interspecific behavior
A colonial bird that nests and roosts in groups of a few as one pair to as many as several hundred birds.
One vagrant swift was observed associating with a loose flock of 8-10 Caribbean Martins (Progne dominicensis), possibly attracted by their foraging habits or the insects they were feeding upon. However, the martins repeatedly chased the swift away when it approached (Kepler 1972).
The Virginia opossum (Didelphis marsupialis) has been observed eating eggs from nests and it is likely that other small mammals take nestlings. Peregrine Falcons (Falco peregrinus) are known to wait at colony sites to catch swifts as they enter or leave the colony to feed and collect nest materials (Whitacre 1989).
Whitacre (1989) hypothesized that the minimal construction of many nests could be due to a tradeoff that the adults have made between a solid nest and the risk of predation from falcons incurred by many trips to gather greater amounts of nest materials. This could also impact upon nestling survival as eggs and young are less likely to fall from a more soundly constructed nest.