White-collared Swifts nest colonially in horizontal or vertical caves, often with a stream or behind a waterfall. Nests are found on ledges and knobs on the face of overhangs, or in niches and potholes beneath the overhangs of the waterfall or ledges over a stream (Whitacre 1989).
The nest is on a broad, flat surface, and often are located in the fine spray of water from the waterfall behind which the nest is located; nest sites also often are in very dark locations inside the cave (Marín and Stiles 1992).
Nests are essentially circular disk shaped constructions of mud, moss and insect chitin; one pair did not construct a nest at all, but laid two eggs on a bed of soft sand (Marín and Stiles 1992). The size of the nest is 120-170 mm in diameter with a depths of 30-90 mm (Rowley and Orr 1965, Whitacre 1989). Different colonies have been observed to have nests made of different materials. For example, a colony behind a waterfall in Chiapas, Mexico had nests constructed mainly of moss, with little mud or insect chitin. Saliva is not used as a nest material (Marín and Stiles 1992). These nests were lined with fresh leaves and/or fern fronds, it was noted that more fresh vegetation was used when the eggs were close to hatching as opposed to when incubation began. If nests are undisturbed, they often are reused each year with additions or modifications (Rowley and Orr 1965).
Nest-building behavior involves picking moss from the cave wall while sitting in the nest, climbing the cave wall to pick moss and bringing nest materials in from outside the colony. One swift was observed flying into the nest cave with a golf ball sized wad of nesting materials in its bill (Whitacre 1989).
White-collared Swifts lay two white eggs that often become mud stained. The nestling period is 45-55 days (Marín and Stiles 1992). Breeding is in late April- early May in south Mexico. Similarly, egg-laying in Costa Rica is late April to mid-May (Marín and Stiles 1992).