EFFECTS OF MACROHABITAT AND MICROHABITAT ON NEST-BOX USE AND NESTING SUCCESS OF AMERICAN KESTRELS

摘要

We studied the nesting ecology of American Kestrels (Falco sparverius) in Berks and Lehigh Counties, Pennsylvania, from 1987-1991. Kestrels used 99 (76%) of 130 nest boxes dispersed throughout a 1000-km~2 study area. A total of 259 nesting attempts was noted: 67, 53, 49, 35, and 55 in 1987, 1988, 1989, 1990, and 1991, respectively. Of the 259 nesting attempts, 124 (49%) successfully fledged at least one offspring. We measured five macrohabitat and 14 microhabitat variables at the 130 nest boxes. Ten (53%) variables were correlated to levels of nest-box use and nesting success. Kestrels most frequently used nest boxes with high nestling-light intensity (P = 0.02) and low nest-box concealment (P = 0.05). Frequently used boxes were associated with extremely open habitat dominated by herbaceous vegetation (P < 0.005). Nesting kestrels avoided using boxes associated with dense habitats, such as late-successional old fields. Frequently used nest boxes were farther from forested areas than unused boxes (P = 0.05). Nest boxes with southeast orientations were used more frequently than expected (P < 0.025), and all other orientations were used in proportion to availability. Kestrels had the greatest nesting success when using nest boxes with high selection-light intensities (P = 0.05).