Ecology of an Urban Population of the Slaty-Backed Gull (Larus schistisagus) in Comparison with Natural Colonies: 1. Features of Nest Location and Productivity

Abstract

The first study of a series of papers analyzing the results of a 14-year-long (2004–2017) monitoring of a Slaty-backed Gull population nesting on the roofs in the city of Magadan is presented. Certain peculiarities of the nesting of one of the first urbanized gull populations in northeastern Asia are revealed. As for urban gulls, in contrast to natural nesting, single-pair locations predominate, but the main number of nests is concentrated in several large colonies. When choosing a city as a breeding ground, gulls move increasingly far inland from the sea coast over the years. The location of bird pairs on new sites in the city usually occurs within the sight of the old colony. The growth rate of the colonies averages 13% per year, this being similar to urban gull populations in Europe. The productivity of urban Slaty-backed Gulls nesting on roofs is much higher than in natural colonies. In the urbanized population, there is neither intraspecific predation on eggs nor the death of chicks from neighbor gulls. Most of the nests of urban gulls are built in the same place for many years. The purpose of a construction determines the degree of attendance of its roof by people, this being crucial for the selection of a nesting site by gulls. As a rule, nests are built either around some obstacle on a roof (walls, pipes, superstructures etc.) or in an absolutely open place. The latter strategy is more typical of single pairs. The safety of roofs from predators seems to be the determinative factor that contributes to the urbanization of gulls.