Written by: C. Polite, G. Ahlborn
Reviewed by: S. Bailey
Edited by: S. Bailey

DISTRIBUTION, ABUNDANCE, AND SEASONALITY

     Common resident throughout California, wintering in all habitats except high elevations.
Also a winter migrant.  Fairly common on Channel Islands.  Occurs in most open habitats, in a
variety of shrub and early successional forest habitats, in forest openings, and various
ecotones.

SPECIFIC HABITAT REQUIREMENTS

   Feeding:    Takes small mammals, birds, insects, earthworms, reptiles, and amphibians.
Perches and pounces, pounces from a hover, or catches flying insects.  Rarely pursues prey
on wing.  Caches prey near nest in cracks in trees or rocks (Collopy 1973).  Perch may be
tree, snag, rock, utility pole or wire, fence post (Grinnell and Miller 1944).  Forages in open
habitats.

   Cover:    Seeks cover in a variety of cavities in trees, snags, rocky areas, banks, and
buildings.

   Reproduction:    Nests in cavities in trees, snags, rock crevices, cliffs, banks, and buildings.
Bent (1938) reported nests in cavities in sycamores, willows, and cottonwoods.  Does not
construct a stick nest.  Often uses cavities excavated by northern flickers and Lewis'
woodpeckers.  In Oregon, Thomas (1979) estimated that the minimum dbh tree required by
these 2 woodpeckers was 31 cm (12 in) and 38 cm (15 in), respectively.

   Water:    Drinks water in captivity (Roest 1957).  Has a high tolerance to heat and aridity.

   Pattern:    Forages in open and partially open areas of most habitats.  Needs cavities near
foraging areas.

SPECIES LIFE HISTORY

   Activity Patterns:    Yearlong, diurnal activity.

   Seasonal Movements/Migration:    At higher elevations, moves downslope for winter and
upslope for summer.  Individuals from north migrate into California for winter (Grinnell and
Miller 1944).  Residents often maintain pair bond throughout the year.

   Home Range:    Prebreeding home range twlce as large as breeding home range on the
east side of the Sierra Nevada (Balgooyen 1976).  At various other locations, winter home
ranges varied from 154-452 ha (380-1117 ac) (Enderson 1960, Mills 1976).

   Territory:    Balgooyen (1976) reported that 32 territories averaged 109 ha (270 ac).  In the
Los Angeles area, Cade (1955) reported that defended territories averaged 10 ha (25 ac).  In
various locations, summer breeding territories varied from 78-399 ha (192-987 ac) (Enderson
1960, Mills 1976).

   Reproduction:    Breeds from early April to August, with peak activity May and June.  Eggs
laid mid-May to late June.  Average clutch size 4-5, range 3-7.  Incubation 28-31 days; young
fledge after 29-31 days.

   Niche:    May be preyed upon by larger raptors.  Balgooyen (1976) suggested that tree
squirrels may destroy nests.  May compete with other cavity nesters: woodpeckers, starlings,
owls, bluebirds, nuthatches, chipmunks, squirrels.  Female larger than male, allowing pair to
partition food resources more effectively.  Ectoparasites include lice, black flies (Roest 1957),
calliphorid flies, and milichiid flies (Balgooyen 1976).

REFERENCES

Balgooyen, T. G.  1976.  Behavior and ecology of American kestrel (Falco sparverius L.) in
     the Sierra Nevada of California.  Univ. Calif. Publ. Zool.  103:1-87.
Bent, A. C.  1938.  Life histories of North American birds of prey.  Part 2.  U.S. Natl. Mus. Bull.
     170.  482pp.
Cade, T. J.  1955.  Experiments on winter territoriality of the American kestrel (Falco
     sparverius).  Wilson Bull.  67:5-17.
Collopy, M. W.  1973.  Predatory efficiency of American kestrels wintering in northwestern
     California.  Raptor Res.  7:25-31.
Enderson, J. H.   1960.  A population study of the sparrow hawk in east-central Illinois.
     Wilson Bull.  72:222-231.
Grinnell, J., and A. H. Miller.  1944.  The distribution of the birds of California.  Pac. Coast
     Avifauna No. 27.  608pp.
Mills, G. S.  1976.  American kestrel sex ratios and habitat separation.  Auk  93:740-748.
Roest, A. I.  1957.  Notes on the American sparrow hawk.  Auk  74:1-19.
Thomas, J. W., ed.  1979.  Wildlife habitats in managed forests:  The Blue Mountains of
     Oregon and Washington.  U.S. Dept. Agric., For. Serv., Portland, OR. Agric. Handb. No.
     553.  512pp.
 
Compiled from information from California Department of Fish and Game - California Interagency Wildlife Task Group