Studies on the herring gull population in North Yorkshire

A census of .Herring Gulls (Larus argentatus) breeding along the Cleveland and Yorkshire coast was conducted during 1978 and 1979. Herring Gulls present between Redcar and Black Nab, south of Whitby and between Black Nab and Filey Brigg were observed throughout the year July 1978 to July 1979. The Herring Gulls observed included a proportion with colour-rings on their legs. Ringing of Herring Gulls was carried out both in the study area and north of it from 1976 onwards by a team from the University of Durham Zoology department. Population estimates are obtained from the census of breeding Herring Gulls as well as from 'mark and recapture’ observations throughout the year. Movements of the Herring Gulls are examined together with the distances of these movements. The behaviour of 1st and 2nd year Herring Gulls is compared with that of Herring Gulls older than 2 years. The data from the census of breeding Herring Gulls, the population estimates and the movement data are compared with data previously obtained in this and other areas by other authors to obtain colony growth rates and establish immigration and emigration patterns to and from the area of study. The rates of increase and the movements throughout the year observed in the study area are discussed