Habitat Selection and Nesting Biology of Roof-Nesting Glaucous-Winged Gulls

Publisher Website
Google Scholar
Abstract
The number of nests, habitat selection, and aspects of the breeding of Glaucous-winged Gulls (Larus glaucescens) on roofs along the waterfront in downtown Vancouver, British Columbia, Canada, were investigated. We investigated that 500 pairs nested in downtown Vancouver in 1986. The number of gulls is expanding in Vancouver and elsewhere along other urban waterfronts in the region. Gulls preferred to nest near water whether other gulls were already established. They either nested in small colonies or built scattered, relatively isolated nests of flat roofs of buildings, and on flat portions or near structures on peaked roots (dispersed nesting). Dispersed gulls nested significantly more often near structures than did gulls nesting in a colony, perhaps because of a limited choice of nest sites at the latter. Egg volumes of early layers were significantly larger than those of late layers in the colony, but the volumes of eggs of early and late dispersed layers were similar. Egg volumes of late nesting colonial birds were signficantly smaller than were those of both early and late dispersed layers. Gulls in the colony may have been mostly older birds laying early, and young and inexperienced ones laying late. Dispersed nesters were most likely to be experienced breeders. Gulls in the colony produced signficantly less young than did dispersed nesters. One of the main causes of mortality in the colony was attacks by adult gulls on chicks, which apparently resulted from high nesting density, which was conductive to frequent territorial clashes, and the general lack of places for chicks to hide from attacks of adult gulls.

This publication has 0 references indexed in Scilit: