Establishing a Nest Box Program for the American Kestrel at the Merced Vernal Pools and Grassland Reserve

In spring 2014, we initiated a nest box project to expand American Kestrel nesting populations and to monitor their breeding success on U.C. Merced’s Vernal Pool and Grassland Reserve. We had observed kestrels foraging on 45 of 105 bird surveys conducted in the 2,656 ha Reserve in 2013 and 2014, but there was no evidence of nesting. Suitable nest sites were lacking so we erected ten nest boxes and monitored them on 14 May, 22 May, 5 June, and 9 June to determine clutch size, hatching success, fledging success, and overall productivity. Six of ten boxes were occupied by adults, and a total of 22 eggs were laid. Clutch size averaged 3.67 eggs. Fifteen eggs hatched, a 68% hatching success rate. Mean number of hatchlings per successful nest was 3.75. Fifteen chicks successfully fledged (100% fledging success). Five young fledged from two nests. Mean nesting success was 67% and nesting productivity averaged 2.5 young fledged per occupied nest. All chicks and four adults were banded. Our study demonstrates that American Kestrels can occupy nest boxes quickly when these artificial nest sites are made available and productivity can be quite high, at least in the initial season of nest box placement.