Propagation of captive American kestrels

A colony of kestrels (Falco sparverius) was established at the Patuxent Wildlife Research Center in 1964 in connection with work on pesticides. The kestrels were acquired from the wild, both as nestlings and as full-grown birds, and were housed in several rows of outdoor pens. Each 50 X 20 ft pen was covered with wire netting and had its long sides in common with adjacent pens. During the first two reproductive seasons, untreated parent birds (dosed birds are not included in this paper) ate eggs and young. Cannibalism virtually ceased after the diet was changed from ground beef or horsemeat supplemented with liver, vitamins, and minerals to one containing a finely ground mixture of laboratory rodents, chicken heads, skinned chicken necks, and supplements; hatching success thereafter generally equalled that of a wild population. In 1967, 16 pairs of untreated hawks (3-year-old females) laid clutches averaging 4.9 eggs, hatched 88 percent of their eggs, and fledged 88 percent of their young. In 1968, 10 pairs of this group (4-year-old females) laid clutches averaging 4.9 eggs, hatched 51 percent of their eggs, and fledged 85 percent of their young. Nine yearling pairs (hatched in captivity) laid clutches in 1968 averaging 5.1 eggs, hatched 87 percent of their eggs, and fledged all of their young. In 1964 a colony of American kestrels was established at Patuxent Wildlife Research Center to test the effects of organochlorine pesticides on the reproduction of this species. Because pesticides reduced the reproductive success of dosed birds (Porter and Wiemeyer 1969), the present paper includes only data from experimental birds fed untreated food, and data from additional birds not involved in the pesticide experiment. The smaller falcons (Falco spp.) have shown a propensity towards breeding in captivity. Two pairs of American kestrels housed in outdoor pens in Germany from 1961 through 1968 raised 61 young, and two males and four females of the second generation raised six young (Koehler 1968: 28-29). Willoughby and Cade (1964:8990) kept six pairs of kestrels in indoor breeding rooms in 1962; the kestrels fledged two young. Two pairs of captive European kestrels (F. tinnunculus) bred by Koehler (1968:30) in 1967 and 1968, raised 14 young. A number of additional records of kestrels nesting successfully in captivity have been compiled by Koehler (1968). Among the larger falcons, both the pere594 grine (F. peregrinus) (Waller 1968, Peterson 1968) and the prairie falcon (F. mexicanus) (Kendall 1968) have hatched eggs and reared young successfully in captivity. The Patuxent colony was established, and the pens were equipped by W. H. Stickel and F. C. Schmid. Their experience and advice provided us with important background when the kestrel research became our responsibility in February, 1967. L. N. Locke, histopathologist at Patuxent, autopsied a number of the birds. J. A. Newman, Department of Veterinary Science, University of Maryland, conducted bacteriological studies to help determine causes of embry nic mortality. The Forest Glen Annex of the Walter Reed Army Medical Center and the National Institutes of Health provided the rodents used in the kestrel diet. L. C. Goldman, photographer, U. S. Bureau of Sport Fisheries and Wildlife, provided the photograph.