AMERICAN KESTREL BREEDING HABITAT: THE IMPORTANCE OF PATCH SIZE

Previous studies have examined vegetative cover and land use immediately surrounding American Kecstrel (Falcos sparverius) nest sites. However, the relatinship of landscape-level habitat, structure to nest-site selection has reccived little attention. Between 1995 and 2007 we crected nest boxcs in pastures and meadows in northwestern New Jersey. The number of breeding pairs in boxes ranged from 2 in 1995 to 59 in 2002. We used a Geographic Information System to model habitats used by kestrels (open areas dominated by herbaceous vegetation) and delineated patches of contiguous suitable habitat wihtin the study arey and statewide. Nest boxes available in large (> 1000 ha) patches of suitable habitat were occupied by kestrels at rates significantly higher than those in medium (250-1000 ha) or small (<250 ha) patches. Large patches exhibited relatively high occupancy rates every year, medium patches were most likely to be occupied during years when kestrels were abundant in the study are, and small patches were used infrequently, regardless of how many breeding pairs were present in the study area. That kestrels disproportionately select nest sites in contiguous patches sufficiently large to include many breeding territories has important implications for conservation strategies. We currently are using information on patch size to implement a statewide nest-box program for kestrels in New Jersey.