Masters Thesis

Landscape characteristics surrounding White-tailed Kite nest sites in southwestern California

I quantified landscape variables surrounding 31 white-tailed kite (Elanus leucurus) nest sites and compared them with 31 unused sites in an undeveloped landscape in southwestern California. Using a geographic information system, I combined landcover data from Orange County with aerial photography to produce a landcover map surrounding white-tailed kite nest sites. Habitat types were quantified and landscape pattern indices were computed within circular plots of 300, 500, 700 and 1000 m radii centered on nests. At all circular scales, kite nests had significantly more agriculture, grassland, riparian, and woodland habitat, and significantly less chaparral habitat than unused sites (P < 0.01). The landscape surrounding nest sites also had significantly greater patch density than unused sites, suggesting a preference for patchier landscapes. All nests were within 307 m of a riparian corridor, and were located at elevations below 314 m, and on slopes less than 25 degrees. I used logistic regression analysis to develop a predictive model of landscape variables that best discriminated between white-tailed kite nest sites and unused sites within my study area. Largest patch index and perimeter density were used to further interpret the landscape surrounding white-tailed kite nests. The final model incorporated distance to nearest stream, percent grassland, and percent woodland, and correctly classified 97% of kite nest sites within the study area. While landscape variables were significantly different between nest sites and unused sites, some variables varied widely among individual kite nest sites. These results suggest that the quality of similar habitat types varied widely across the landscape, and that the quantity of habitat necessary to support a pair of nesting kites may vary as well. For white-tailed kites in California, habitat quality is largely dependent on abundance and availability of California voles (Microtus californicus).

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