The Biology of the American Kestrel in Central Utah

Hawks, eagles, & falcons of North America: biology and natural history

“…Balgooyen reported a high hatching rate of 89 percent, followed by an even more remarkable 98 percent fledging success, or an overall reproductive success of 87.5 percent. A somewhat smaller but still impressive 78 percent hatching success was reported by Heintzelman and Nagy (1968), while Smith, Wilson, and Frost (1972) estimated a 67 percent hatching success and a 72 percent fledging success in Utah. Renesting following initial clutch losses is known to be frequent, and such efforts may increase the overall productivity somewhat (Bowman and Bird, 1985).…”

“…Pair bonding in kestrels is strong and tends to be permanent. Craighead and Craighead (1956) found a pair nesting in the same tree cavity for six consecutive years; 26 of 31 pairs studied in Utah (Smith, Wilson, and Frost, 1972) maintained their territories during two consecutive years, and 21 of these did so for three consecutive years, even though only eight pairs used the same nest site all three years. Balgooyen (1976) found that 11 of 18 territories were active a second successive year.…”

“…In Utah, Smith, Wilson, and Frost (1972) found that 19 of 41 nests were in woodpecker holes, 7 in natural cavities, and 13 in niches in rocky cliffs or in buildings. In Ontario, natural sites are more often in deciduous than coniferous trees, in dead rather than in living trees, and in woodpecker cavities than natural cavities.…”

“…Millsap (1981) reported an average nearest-nest distance of 1.1 kilometers in Arizona. A population density of 1.2-1.7 pairs per square kilometer was estimated by Smith, Wilson, and Frost (1972) in Utah; Enderson (1960) estimated a lower breeding density of 0.75 pairs per square kilometer in Illinois.…”

“…The most important vertebrate prey were starlings (Sturn us vulgaris) and deer mice (Peromyscus maniculatus), these two species contributing over 60 percent of the total biomass intake. Smith, Wilson, and Frost (1972) found that vertebrates comprised only 20 percent of the species's foods in. Utah numerically, but made up 96 percent of the total prey biomass, with voles (Microtus spp.)…”