Nests are built on the horizontal rock ledges of cliffs or vertical walls of roosting sites.
Nest building typically begins in October, but varies regionally. Swifts collect nesting material (predominantly lichen, bryophytes, pteridophytes, angiosperms, and soil) using the bill. Nest shape may be circular, ellipsoid, or semicircular. As observed in many other swift species, Biscutate Swift exhibits extreme preference for locations in which previous nesting has occurred (Pichorim 2002). Experimental manipulation of nest sites and vestiges of nests have shown that Biscutate Swift pairs use previous years' nesting material as well as memory to locate these previously used sites (Pichorim et al. 2009).
White, sub-elliptical eggs are laid beginning in November, and all individuals in a colony lay within the same short time frame (8 days in one colony). Clutch size ranges from 1-4 eggs. Studies have suggested that clutch size is directly proportional to the number of eggs swifts are fit to raise. Thus, couples with 4 eggs are thought to be more capable of raising a large brood than are those that lay fewer eggs. If eggs are lost after incubation, nests will be abandoned and no new eggs will be laid (Pichorim 2008, Pichorim 2011)
Incubation lasts around 24 days, and parents share in incubation and feeding. Nestlings are blind and naked upon hatching, and the first feather coat of gray semiplumes is fully established at 13 days. Adult plumage is fully developed by 34 days, and nestlings remain in the nest about 33 days. After fledging, young birds return to the nest for about 10 days (Pichorim 2002).