Nesting occurs in loose colonies, in groups of 2-5 nests, generally 75-700 meters apart (Meyer 1995). In south Florida, nearest nests averaged 673-730 meters apart (Meyer and Collopy 1995). Individuals often nest near sites that were used previously for nesting by swallow-tailed kites. In south Florida, 77 percent of nests sites were re-used and at 23.5 percent of these the original nest was re-used after being re-furbished. However, because birds were unmarked it is not known if sites were re-used by previous residents (Meyer and Collopy 1995).
Nesting occurs February-May in Costa rica and from early March-early June in the United States (Meyer 1995, Meyer and Collopy 1996, Stiles and Skutch 1989). Clutch size ranges from two to four eggs but is typically two (Terres 1991). The average of 151 U.S. clutches was 2.12 eggs, that of 11 Florida clutches was 1.91 eggs, and that of 18 Guatemala clutches was 1.83 eggs (Gerhardt et al. 1997, Meyer 1995). Incubation, conducted principally by the female, takes approximately 28 days in Florida and averages 31.5 days in Guatemala. Incubation begins when the first egg is laid and hatching is asynchronous (Gerhardt et al. 1997, Snyder 1974). The young are brooded by both sexes, although principally by the female. The nestling period is 36-42 days (Snyder 1974). There is no evidence of second-clutching even after nest or egg failure (Meyer 1995). Brood reduction sometimes occurs when younger nestlings starve or are killed outright by larger nestlings (Gerhardt et al. 1997, Meyer 1995).
Estimates of nesting success (percent of nests that fledged greater than or equal to 1 young) include 33 percent for Guatemala (Gerhardt et al. 1997), 41-80 percent for Florida (Meyer and Collopy 1995), and 72 percent for South Carolina (Cely and Sorrow 1990). Productivity estimates (number of young fledged per nest) for these same studies vary from 0.33 (Guatemala), 0.48-1.27 (Florida), to 1.14 (South Carolina). In Florida, nest success varied by species of nest tree: 78 percent for cypress, 60 percent for slash pine and 17 percent for Australian pine. In addition, nests in more flexible trees failed more often due to wind than nests in more rigid trees (Meyer and Collopy 1995).
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