The Effects of Car Traffic on Breeding Bird Populations in Woodland. I. Evidence of Reduced Habitat Quality for Willow Warblers (Phylloscopus trochilus) Breeding Close to a Highway

Abstract

This study investigated the effect of a highway with dense traffic on the quality of adjacent habitats for the willow warbler Phylloscopus trochilus. In the zone of 0-200 m from the highway (road zone) the density of territorial males was much lower (2.1 ha −1 ) than in zones with a comparable habitat at a greater distance (3.3 ha −1 ). The lower density in the road zone was due to a low presence of older males. As a consequence, the proportion of yearling males in the road zone was about 50% higher than in the other zones. Yearling males occupied their territories in the road zone later than in the other zones. In the road zone the proportion of successful yearling males was about 50% lower than in the other zones. No difference was observed in the number of nestlings per male