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Nest-site characteristics and linear abundance of cliff-nesting American kestrels on San Clemente Island, California

January 1, 2003

American Kestrels( Falco sparverius) are typically secondary-cavity nesters, and use of natural
cliff cavities for nest sites is less-commonly reported. On San Clemente Island (SCI), California, however, American Kestrels nest primarily on cliffs in major canyons(93%), to a lesser extent on seacliffs(4%), as well as in man-made structures (3%). We located and mapped 99 American Kestrel territories on SCI, and recorded 11 nest-site characteristics at 40 cliff nests during 2001-02. Nest cliffs were typically fractured igneous rock with mean height of 16.1 m +_ 1.8 SE. Mean slope of nest cliffs was vertical (x=91 degrees). Nest cliffs and cavities were significantly oriented to the southeast, away from the prevailing wind direction(NW). In eight canyons, where we believe that we found all occupied American Kestrel territories, the mean linear abundance was 2.1 pairs/km, greater than most published estimates. Contrary to most previous studies, no American Kestrels nested in tree cavities despite their presence in SCI canyons. The absence of cavity-excavating breeding birds from the island likely restricts kestrels to nesting in naturally-formed cavities and man-made structures.

Publication Year 2003
Title Nest-site characteristics and linear abundance of cliff-nesting American kestrels on San Clemente Island, California
Authors Brian L. Sullivan, Eric L. Kershner, S.P. Finn, Anne M. Condon, Douglass M. Cooper, David K. Garcelon
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Raptor Research
Index ID 1016300
Record Source USGS Publications Warehouse
USGS Organization Forest and Rangeland Ecosystem Science Center