Most individuals do not nest until two-years old (Dexter 1981a, Fischer 1958).
OVIPOSTION/INCUBATION: Eggs are laid from May through July (Terres 1991). Nests are constructed of dead twigs broken off trees while birds are in flight (Shelley 1929) and glued to the interior wall of a hollow anthropogenic or natural structures with saliva (Bent 1940, Fischer 1958). Old nests are rarely re-used (Dexter 1962, Dexter 1981b). Egg-laying begins when the nest is approximately half finished. Egg are laid every other day and incubation begins after the penultimate egg is laid. Clutch size typically ranges from 2-6 eggs (average = 4.3), but as many as 8 eggs have been found in one nest. Nests containing more than six eggs may be the result of oviposition by two females. Incubation typically takes 19 days, but ranges from 16-21 days. Will re-lay if first clutch is lost (Fischer 1958). One female, studied over a 10-year period, laid a total of 34 eggs (3-5 eggs per clutch, mean = 4.25, n = 8) and fledged 27 young (0-4 young per year, mean = 3, n = 9; Dexter 1956). Clutch size of first-year nesting females (2-5 eggs, mean 3.5) studied in Ohio was smaller than subsequent clutches (3-7, mean 4.1; Dexter 1981a). Both sexes incubate the eggs and brood and feed the young. An additional adult or two sometimes assist parents with incubation, brooding and feeding of young (Dexter 1952a, Fischer 1958). The extra adult is most often a male (Dexter 1952a, Dexter 1981a). Whereas extra adults enhanced nesting success of first-year nesting females, they had no influence on nesting success of older females (Dexter 1981a).
FLEDGING: Young leave the nest, but remain nearby, at 14-19 days old. Juveniles typically first fly 30 days after hatching.
NEST SUCCESS: Hatching success for 20 nests studied in New York was 90.7%, and fledging success, as defined as young that survived to fly outdoors, was 86% (Fischer 1958). Adults continue to care for young washed out of the nest and, in some cases, the young survive to fledge (Dexter 1952b).