Ed Harper Habitat Use Profile Habitats Used in California Variety of open habitats (including desert), such as irrigated pasture, alfalfa and other forage crops, grasslands, oak savanna 1, in winter females dominate in best habitats (alfalfa, irrigated pasture, wet coastal grasslands) 2,3,4 Key Habitat Parameters Plant Composition Plant Density/structure Mosaic Minimum Patch Size Home Range No particular plant composition favored Prefers areas with fairly low vegetation where prey is visible and accessible 1,3,5 Highly generalized in winter; requires nest cavities (natural or man-made) 1 or cliffs 6 during breeding season Area Requirements Unknown in CA but studies in New Jersey suggest patches >1000 ha may be ideal 7 Little studied in CA but probably much less than 500 ha 8,9,10, winter range larger than breeding season 8 American Kestrel Conservation Profile Species Concerns Loss of grassland & compatible ag habitats to intense ag, urban uses 3 ; exposure to pesticides and other environmental contaminants; declines seen range-wide Continental PIF Audubon Watchlist IUCN USFWS BLM USFS DFW CBC BBS California US/Canada California as % of US/Canada Source Coverage in CA Protection Other Rankings Least Concern California Population Trends Negative (significant) 11 Negative (significant) 12 Population Size Estimates 19-23,000 13 (Central Valley), 240,000 14 240,000 15, 800,000 13, 2,200,000 14 Approx 10% 14 Population Objective Maintain/Increase Monitoring Coverage CBC BBS ebird Good CBC coverage, fair BBS coverage Key Conservation Areas Highest breeding & winter densities probably in southern Sacramento and northern San Joaquin valleys, where dependent on compatible ag uses Natural History Profile Seasonal Presence in California Year-round with influx of birds from elsewhere in winter Known Breeding Dates in California Not well-studied in CA, but likely April-June 1,8, extending into July if second brood produced 1 Nest Placement Site Fidelity Basic Nest and Nesting Habits Cavity in tree, nest box or other man-made structure 1,8,16, nesting extensively on cliffs on San Clemente Island 6 Low to moderate fidelity to breeding and winter sites 1, in Idaho, low natal fidelity to site, moderate to general area 17 Food Habits Typically hunts from a low perch (utility line or fence) 1,18,19, less often from hover 19 Primary Diet Wide variety of large insects, small rodents, birds, and reptiles 1 Confidence in Available Data: High Moderate Low
Overview While still common and widespread, American Kestrels have shown long-term, highly significant decline throughout their range, even in areas where the habitat appears intact. Range: Found year-round throughout California in all but the highest altitudes or densest urbanized areas. Historic Range: Historic range probably similar to current except for areas of intense urbanization. Response to Management: Nest boxes in any suitable foraging habitat may be readily used. Abundance and Occupancy by Habitat Capable of nesting in high densities (mean territory size of 100 ha in eastern Sierra 8, linear abundance of 2 pairs/km along cliff faces on San Clemente Island 7 ) where cavities or other nest sites are present in suitable foraging habitat.
California-Specific Studies and Analyses Surprisingly little recent work on nesting ecology in the state. Author Main Findings/Content Type of study Balgooyen Study of ecology of kestrels breeding in the Observational 1976 eastern Sierra Bloom and Hawks 1983 Study of next box use in Lassen County Observational Collopy Study of foraging behavior in northwestern CA Observational 1975 Koplin 1983 Study of winter habitat use by sexes in northern Observational CA Pandolfino Study of winter habitat associations in the CV Observational et al. 2011a Pandolfino Study of winter habitat use by sexes in the CV Observational et al. 2011b Smallwood and Bird 2002 Overview of behavior, range, nesting, diet, habitat, threats, population trend, demographics, and management issues throughout the range Review Smallwood et al. 2009a,b,c Sullivan et al. 2003 Study of mortality due to wind turbines in Altamont Pass Study of cliff-nesting on San Clemente Island Observational Observational
Main Threats and Challenges Habitat and Other Threats Conversion of grassland and compatible farming (e.g. alfalfa) to more intense agriculture (vineyards, orchards), urbanization Reduction of insect prey due to pesticide use Lack of nesting cavities and competition for those sites with other species such as European Starlings Best agricultural habitats require access to water so increasing demands for water may affect extent of such habitats Exposure to environmental contaminants. A large and growing body of research suggests that a number of chemicals used as flame retardants affect American Kestrel reproduction and are found in kestrels at high concentrations. Some recent examples are cited. 20,21,22,23 However, a direct link to declining kestrel numbers is difficult to confirm. Recent increases and range expansions of Common Ravens may pose a growing threat to American Kestrels in California Wind energy projects 24 Research, Planning, and Monitoring Challenges More research is needed on breeding productivity and ideal habitat characteristics, so that preservation can be targeted to the best sites. The long-term, widespread declines in American Kestrels, even in areas with intact habitat, suggest that environmental contaminants may be a key factor. If so, persistence of such chemicals may confound conservation efforts. American Kestrels are fairly easy to observe and monitor and their use of nest boxes makes studies of reproductive success practical.
Conservation Strategies Management Strategies Provide nest boxes in areas with good foraging potential Reduce use of pesticides within areas of high kestrel use Research, Planning, and Monitoring Strategies Monitoring nest boxes is an efficient means for assessing local reproductive success Determination of habitat characteristics which support high concentrations of American Kestrels. Winter habitats with high proportions of female kestrels are likely to represent the best habitats Continued work on the presence and affect of specific environmental contaminants such as flame retardants Public Outreach Strategies Work with landowners to encourage farm practices that support foraging habitat for American Kestrels and to allow placement and monitoring of nest boxes Use citizen science approaches to fund nest box programs and to assist with monitoring Use public pressure to enhance control (or banning) of suspect environmental contaminants Work with future wind energy projects during the planning and pre-construction phase to ensure least-hazardous placement of turbines on the landscape.
References: American Kestrel 1 Smallwood and Bird 2002 2 Koplin 1973 3 Pandolfino et al. 2011a 4 Pandolfino et al. 2011b 5 Collopy 1975 6 Sullivan et al. 2003 7 Smallwood et al. 2009d 8 Balgooyen 1976 9 Mills 1976 10 Bird and Palmer 1988 11 National Audubon Society 2010 12 Sauer et al. 2012 13 Pandolfino and Smith 2011b 14 Partners in Flight Science Committee 2013 15 Johnsgard 1990 16 Bloom and Hawks 1983 17 Steenhof and Heath 2013 18 Collopy 1975 19 Bildstein and Collopy 1987 20 Sullivan et al. 2013 21 Rattner et al. 2013 22 Marteinson et al. 2012 23 Chen et al. 2012 24 Smallwood et al. 2009c Balgooyen, T. G. 1976. Behavior and ecology of the American Kestrel (Falco sparverius) in the Sierra Nevada of California. Univ. Calif. Publ. Zool. 103:1-83. Bildstein, K. L. and M. W. Collopy. 1987. Hunting behavior of Eurasian (Falco tinnunculus) and American Kestrels (F. sparverius): a review. Pages 66-82 in The ancestral kestrel. (Bird, D. M. and R. Bowman, Eds.) Raptor Res. Rep. 6. Bird, D. M. and R. S. Palmer. 1988. American Kestrel. Pages 253-290 in Handbook of North American birds. Vol. 5: diurnal raptors. Pt. 2. (Palmer, R. S., Ed.) Yale Univ. Press, New Haven, CT.
Bloom, P. H. and S. J. Hawks. 1983. Nest box use and reproductive biology of the American Kestrel in Lassen County, California. Raptor Res. 17:9-14. Chen, D., R. J. Letcher, and P. Martin. 2012. Flame retardants in eggs of American Kestrels and European Starlings from southern Lake Ontario region (North America). J. Environmental Monitoring 14:2870-2876. Collopy, M. W. 1975. Behavioral and predatory dynamics of American Kestrels wintering in the Arcata Bottoms. M.S. thesis. Humboldt State University, Arcata, California. Johnsgard, P.A. 1990. Hawks, Eagles, and Falcons of North America. Smithsonian Institute Press, Washington, D.C. Koplin, J. R. 1973. Differential habitat use by sexes of American Kestrels wintering in northern California. Raptor Res. 7:39-42. Marteinson, S. C., D. M. Bird, R. J. Letcher, K. M. Sullivan, I. J. Ritchie, and K. J. Fernie. 2012. Dietary exposure to technical hexabromocyclododecane (HBCD) alters courtship, incubation and parental behaviors in American Kestrels (Falco sparverius). Chemosphere 89:1077-1083. Mills, G. S. 1976. American Kestrel sex ratios and habitat separation. Auk 93:740-748. National Audubon Society. 2010. The Christmas Bird Count Historical Results [Online]. Available http://www.christmasbirdcount.org [accessed Dec 2013]. Pandolfino, E. R., M. P. Herzog, S. L. Hooper, and Z. Smith. 2011a. Winter habitat associations of diurnal raptors in California's Central Valley. Western Birds 42:62-84. Pandolfino, E. R., M. P. Herzog, and Z. Smith. 2011b. Sex-related differences in habitat associations of wintering American Kestrels in California's Central Valley. Journal of Raptor Research 45:38-45. Pandolfino, E. R. and Z. Smith. 2011b. Central Valley winter raptor survey (2007-2010): Winter raptor population estimates. Central Valley Bird Club Bulletin 14:66-76. Partners in Flight Science Committee 2013. Population Estimates Database, version 2013. Available at http://rmbo.org/pifpopestimates. [accessed Jan 2014]. Rattner, B. A., R. S. Lazarus, G. H. Heinz, N. K. Karouna-Renier, S. L. Schultz, and R. C. Hale. 2013. Comparative embryotoxicity of a pentabrominated diphenyl ether mixture to Common Terns (Sterna hirundo) and American Kestrels (Falco sparverius). Chemosphere 93:441-447.
Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, D. J. Ziolkowski, Jr., and W. A. Link. 2012. The North American Breeding Bird Survey, Results and Analysis 1966-2011. Version 07.03.2013 USGS Patuxent Wildlife Research Center, Laurel, MD. Smallwood, J. A. and D. M. Bird. 2002. American Kestrel (), no. 602, The Birds of North America Online (A. Poole, Ed.). Cornell Lab of Ornithology. [accessed Jan 2014]. Smallwood, K. S., L. Neher and D. A. Bell 2009a. Map-based repowering and reorganization of a wind resource area to minimize burrowing owl and other bird fatalities. Energies 2(4):915-943. Smallwood, K. S., L. M. Rugge, and M. L. Morrison. 2009b. Influence of Behavior on Bird Mortality in Wind Energy Developments. J. of Wildlife Management 73(7):1082-1098. Smallwood, K. S., and B. Karas. 2009c. Avian and Bat Fatality Rates at Old-Generation and Repowered Wind Turbines in California. J. of Wildlife Management 73(7):1062-1071. Smallwood, J. A., P. Winkler, G. I. Fowles, and M. A. Craddock. 2009d. American Kestrel breeding habitat: The importance of patch size. J. Raptor Res. 43:308-314. Steenhof, K. and J. A. Heath. 2013. Local Recruitment and Natal Dispersal Distances of American Kestrels. Condor 115:584-592. Sullivan, B. L., E. L. Kershner, S. P. Finn, A. M. Condon, D. M. Cooper, and D. K. Garcelon. 2003. Nest-Site Characteristics and Linear Abundance of Cliff-Nesting American Kestrels on San Clemente Island, California. J. Raptor Res. 37:323-329. Sullivan, K. M., S. C. Marteinson, R. J. Letcher, J. Robert, D. M. Bird, I. J. Ritchie, J. L. Shutt, and K. J. Fernie. 2013. Changes in the incubation by American Kestrels () during exposure to the polybrominated diphenyl ether (PBDE) mixture DE-71. J. Toxicology and Environmental Health 76:978-989.