More info for the terms: cacti, natural, tree
American kestrels occupy a wide variety of open to semiopen habitats,
including farmland and urban areas from sea level up to 13,000 feet
(3,960 m) elevation [29,40]. They generally occur in any habitat that
contains an adequate prey base, perch sites, and (during the nesting
season) nesting sites [40]. In the Sierra Nevada, American kestrels
range up to alpine zones, mountain meadows, and other open areas in late
summer and fall, but winter at lower elevations [54]. In Montana, they
breed at forest edges and in groves, ranging out over adjoining
prairies, croplands, and badlands [40]. In Nevada, the highest
densities of both breeding and wintering American kestrels are often
located near agricultural areas or riparian vegetation that support an
abundant prey base. Nesting densities in these preferred habitats often
exceeds one pair per square mile [25]. In British Columbia, American
kestrels commonly occupy quaking aspen (Populus tremuloides) groves,
woodland edges, river bottomlands, wooded lakeshores, farmlands, burns,
meadows, orchards, marshes, and bogs [13].
Southeastern American kestrels inhabit mostly open pine forests and
clearings where snags occur [27]. The decrease of isolated or scattered
pine snags in open habitats used by southeastern American kestrels was
closely correlated with the decline in the number of breeding pairs
[50].
Nesting habitat - Nest sites are usually located along roadways,
streams, ponds, or forest edges [15]. Nests may be reused from year to
year. In Utah, twelve pairs used the same nest site for 2 consecutive
years and eight pairs used the same site again the third year [24].
Southeastern American kestrels often use the same nest site in
successive years [34]. However, Hammerstrom and Hart [23] found that
American kestrels in central Wisconsin did not use the same nest site in
succeeding years even after having raised a brood successfully.
American kestrels prefer to nest in natural cavities with tight-fitting
entrances, or in cavities excavated by other bird species in both live
trees and snags [15,24,29,40]. The diameter of 15 cavity openings used
by American kestrels in British Columbia ranged from 2.5 to 14.1 inches
(6.4-36 cm) [13]. Trees with a d.b.h. greater than 12 inches (30 cm)
are preferred [15]. The species of trees used differs among geographic
regions [13,24,56,58]. Cavities excavated by northern flickers
(Colaptes auratus) and natural cavities located 6.5 to 35 feet (2-10.7
m) above the ground are commonly used as nesting sites [24]. If
cavities are unavailable, American kestrels nest in a variety of sites
including niches in rocky cliffs, under the eaves of buildings, in old
black-billed magpie (Pica pica) nests, in cavities in cacti, in unused
chimneys, or in nest boxes [15,17,24,54].
Herron and others [25] reported that American kestrels in Nevada
generally nest about 20 feet (6 M) from the ground and seem to prefer an
easterly exposure.
Of 41 American kestrel nests in Utah, 28 were located in trees (19 in
old northern flicker holes, two in old magpie nests and seven in natural
cavities). The species and number of trees used were 18 cottonwood
(Populus spp.), 3 poplar (Populus spp.), 3 willow (Salix spp.), 3 maple
(Acer spp.), 1 elm (Ulmus spp.), and one apple. Two of the remaining
nests were located in rocky cliffs and the last 11 were found on
building tops [24]. In southeastern Montana and northern Wyoming, most
American kestrel nests were in cavities of ponderosa pine (Pinus
ponderosa) and cottonwood or in sandstone cliffs. Other nests were in
fenceposts, under bridges, and in abandoned magpie nests. The greatest
number of nests occurred in ponderosa pine stands. The mean distance
between occupied nest sites on the survey plots was 0.4 miles (0.7 km)
[56].
In British Columbia, American kestrel nests were situated in woodpecker
holes or natural cavities in living and dead trees (73%), in man-made
structures (23%), and in holes in cliffs. Sometimes nests of other
species of birds were used, including those of belted kingfishers
(Ceryle alcyon), black-billed magpies, and American crows (Corvus
bachyrhynchos). Ponderosa pine (29%) and Douglas-fir (Pseudotsuga
menziesii) (10%) were the most often used species of coniferous trees;
important deciduous trees were black cottonwood (Populus trichocarpa)
(19%) and quaking aspen (8%). Man-made structures included nest boxes
(17%), buildings, power poles, and fence posts [13].
Nests of southeastern American kestrels are commonly located in old
woodpecker holes in snags 12 to 35 feet (39-114 m) above the ground
[27]. Most nest cavities have been excavated by northern flickers,
red-headed woodpeckers (Melanerpes erythrocephalus), or red-bellied
woodpeckers (Melanerpes carolinus) [58]. In north-central Florida,
southeastern American kestrels nested most frequently in longleaf pine
trees. Turkey oak and live oak (Quercus virginiana) were also occupied.
Natural cavities occurred solely in turkey oak, whereas all nest
cavities in longleaf pine were of woodpecker origin. The frequent use
of longleaf pine in this study indicates that this tree species is
particularly important for southeastern American kestrels nesting in
north-central Florida. Turkey oak snags may be important alternate nest
sites for southeastern American kestrels and may increase in importance
as longleaf pine becomes scarcer [58].
Foraging habitat - American kestrels generally forage in open habitats
that contain high perches [29]. They probably use perch sites in tree
islands and along forest edges. They also hunt by hovering over areas
of short, open vegetation [15]. American kestrels usually search for
prey from elevated perches such as fenceposts, utility poles and wires,
live trees, snags, and rock outcrops [15,36,40]. They prefer perches 16
feet (5 m) high or higher to perches over 8 feet (2.5 m) high [22].
Fischer and others [20] found that American kestrels wintering in
central Utah predominantly used wire perches. Poles and trees were used
less often. In Venezuela, 25 feet (7.6 m) tall poles were more
acceptable for perches than 6 foot tall (1.8 m) poles [40].
Winter habitat - Winter habitat for American kestrels is generally the
same as nesting habitat, except that high elevation areas are not used
[15,29]. Several studies have found
differential habitat use by male and
female adult American kestrels in the southern United States and
northern Mexico. In areas of winter segregation, females often occupy
the best habitats which often includes open areas covered with short or
sparse ground vegetation. Males are found primarily in woodland
openings, along woodland edges, or in other less open habitats. This
differential habitat use may be due to the males arriving on the
wintering grounds later than the females. The females therefore may
establish their winter territories in the best habitats before the males
arrive [46,47].