Behavioral and predatory dynamics of American kestrels wintering in the Arcata bottoms

Thesis (M.S.)--Humboldt State University, Wildlife Management, 1975This thesis reports the results of a study on the time and activity patterns, ecological energetics, predatory efficiency, and caching behavior of American Kestrels (Falco sparverius) wintering in the vicinity of Arcata, Humboldt County, California. Several studies on the time and activity budgets of birds have been conducted in recent years. Most were conducted during the breeding season (Orians 1961, Verner 1965, Schartz and Zimmerman 1971, Verbeek 1972); only two (Pearson 1954, Verbeek 1964) involved wintering birds. The study reported here on the American Kestrel also was conducted during the winter. In this study I monitored the behavioral patterns of single birds not involved in reproductive activities. Some time and activity data were reported for White-tailed Kites (Elanus leucurus) (Stendell 1972, Bammann 1975) and breeding Kestrels (Balgooyen 1972). Ueoka (1974) quantified the time and activity patterns of predatory behavior of Ospreys (Pandion haliaetus) in relation to the breeding season. Levenson (in progress) is studying the time and activity patterns of Ospreys at their nests. Schnell (1967) studied the influence of environmental conditions on the incidence of flight in Rough-legged Hawks (Buteo lagopus). \ud The energy expenditure of raptorial birds in the field has been estimated only for the Snowy Owl (Nyctea scandiaca) (Gessaman 1972). Gessaman (1973) is currently conducting laboratory research which, when perfected, will provide a sophisticated energy budget for the American Kestrel. In the present study, the energy expenditure of Kestrels was predicted following deterministic models developed by Koplin (1972, and in prep.). The predicted energy expenditure was compared with observed caloric intake as a means of testing the valid-' ity of the deterministic model. \ud The efficiency of predators in obtaining prey recently has interested field biologists. The predatory efficiency of Kestrels was studied during the non-breeding season in Costa Rica (Jenkins 1970) and in Michigan (Sparrowe 1972), and during the breeding season in Califor-nia (Balgooyen 1972). Ueoka (1974) reviewed the literature on hunting efficiency of birds and mammals and presented data on the hunting efficiency of Ospreys. Additional studies concerned with hunting efficiency were conducted on White-tailed Kites (Stendell 1972, Bammann 1975), Snowy Owls (Rohn 1974) and several non-raptorial \ud birds (Orians 1969, Dunn 1972, Recher and Recher 1972, Dinsmore 1973, Schlorff in progress). \ud Prey caching has been documented for many raptors. Among falcon - iforms, prey caching has been reported in American Kestrels (Pierce 1937, Tordoff 1955, Roest 1957, Stendell and Waian 1968, Balgooyen 1972, Mueller 1974), Merlins (Falco columbarius) (Greaves 1968), and Goshawks (Accipiter gentilis) (Schnell 1958, Gullion 1965). Prey caching also has been observed in many owls (Allen 1924, Lockley 1938, Wallace 1948, Raber 1950, Mossman 1955, Jansson 1964, Norburg 1964, Grant 1965, Ligon 1968, Catling 1972)