Effects of Researcher-Induced Disturbance on American Kestrels Breeding in Nest Boxes in Northwestern New Jersey

Abstract

Abstract Nest boxes for American Kestrels (Falco sparverius) may alleviate local nest site limitation, but there is concern that periodically opening nest boxes or handling adults may negatively affect nesting success. I monitored 536 kestrel breeding attempts (≥1 egg laid) in about 100 nest boxes in northwestern New Jersey, 1995–2012. To study return rates, I opportunistically captured adults in nest boxes and marked them with U.S.G.S. leg bands and patagial tags. To examine possible effects of this disturbance, I compared nesting success (≥1 nestling surviving to banding age) of marked and unmarked adults. Nesting success was 67% for 270 unmarked pairs, 76% for 25 pairs with only the male marked, 82% for 206 pairs with only the female marked, and 91% for 35 pairs with both adults marked. This significant difference likely reflects differences in the probability of capture: successful attempts last longer and successful parents may be more attentive. To control for these correlations, I examined attempts...