Reproductive Patterns in Captive American Kestrels (Sparrow Hawks)

Abstract

A colony of captive American Kestrels (Falco sparverius) was established in outdoor pens at Patuxent Wildlife Research Center, Laurel, Maryland, in 1964 to investigate effects of pesticides on raptor reproduction. We have reported on the breeding success, clutch size, and management of the colony (Porter and Wiemeyer 1970), on effects of DDT and dieldrin on reproduction (Porter and Wiemeyer 1969), and on effects of DDE on eggshells (Wiemeyer and Porter 1970). In this paper we report on the chronology of egg laying, incubation behavior, duration of incubation and nestling periods, and nestling sex ratios of captive kestrels untreated with pesticides. There are relatively few published accounts on the breeding biology of either captive or wild American Kestrels. Basic reproductive behavior of kestrels housed in indoor pens was investigated by Willoughby and Cade (1964). Heintzelman and Nagy (1968) reported on clutch sizes, success of hatch, and nestling sex ratios of wild kestrels nesting in artificial nest boxes in Pennsylvania. Koehler (1968) gave similar data for captive kestrels of two species (F. s. sparverius and F. tinnunculus) in Germany. Sherman (1913) published detailed observations of the nest life of an Iowa pair. Nesting chronology was reported by Enderson (1960) for Illinois, by Craighead and Craighead (1956) for Michigan and Wyoming, by Roest (1957) for the Pacific Northwest, and by Cade (1955) for southern California. Clutch size, success of hatch, and fledging success also were reported in the Michigan-Wyoming study (Craighead and Craighead 1956). More generalized reproductive data have been summarized by Bent (1938) for the species in the United States and Canada.