The utilisation of urban resources by the herring gull (larus arqentatus)

Abstract

The utilisation of urban resources by the Herring Gull was studied between 1973 and 1976 in Northeast England. This involved a study of refuse tips as a winter food supply, and the use of inhabited buildings as nesting sites. The local breeding population is small, and there is an influx of gulls from east Scottish and Norwegian colonies into Northeast England during the winter months. Herring Gulls caught during winter could be sexed by bill depth alone; wing length was used as an indicator of geographical origin. Gulls fed at refuse tips in the study area throughout the winter months. There was a predominance of adults over immatures at refuse tips in winter, while immatures predominated over adults around inshore fishing vessels in the same area. There was considerable fluctuation in the number of gulls present at tips on different days, related to weather factors and feeding conditions elsewhere. Immature Herring Gulls were less constant to a particular feeding area than adults, and adult females less so than adult males. Individual Herring Gulls did not feed at refuse tips every day, and refuse did not constitute the major or necessarily the only food source for these birds in winter. There were two different feeding areas used by gulls on the refuse tips which differed in the abundance and availability of food: individual birds consistently used one or other area, and proportionally more adult females than males used the secondary area. The number of nesting pairs/ pairs and nest sites used by Herring Gulls nesting on buildings in Sunderland and South Shields were monitored. Their breeding success was higher than in more "natural" colonies, possibly due to the nature of the nesting sites. A national census of gulls nesting on buildings in Britain and Ireland was organised in 1976, to measure the growth and spread of rooftop nesting: the number of Herring Gulls nesting on buildings was found to be doubling within 5 years, and the number of Lesser Black-backs within 3 years. The potential public health hazard presented by gulls nesting on buildings was reviewed.