Effects of nest and colony features on lesser kestrel (Falco naumanni) reproductive success

Abstract

Lesser kestrel is a facultative colonial raptor mostly breeding in man-made structures. During 2009-2011 we checked the fate of 545 nests found in 18 colonies located in south-eastern Sicily. We determined the reproductive success of breeding pairs by analysing the survival time of each egg to hatching (n = 2495) and each nestling to fledging (n = 1849) with the Linear Hazard model of survival times. We determined whether egg and nestling survival differed between years with a Gehan-Wilcoxon test. By Cox regressions, we related the survival times with nest and colony features. Egg and nestling survival times showed a strong annual effect. The two reproductive stages of lesser kestrel when controlled for the annual effect demonstrated a significant effect for some nest and colony features. Most of them, like height from the ground, nest depth, reused nests and the presence of jackdaws, are likely related to the predation pressure faced by lesser kestrel nests. Westward and southward nests had a better egg survival respect to those in the cold sides and in the interior of buildings. The location of colony in the agricultural plain and human disturbance ranked as the most important variables, with core location of a colony and high disturbance levels negatively affecting the reproductive success of lesser kestrel in the Gela Plain, so urging a more environment-aware land use management of this Important Bird Area.