Use of Refuse Tips by Adult British Herring Gulls Larus argentatus During the Week

Abstract

(1) The use of refuse tips by adult herring gulls was investigated using individually marked birds captured in Co. Durham and studied at Coxhoe refuse tip. (2) The pattern of work at the tip greatly influenced the time of gull feeding. Although they rarely fed when lorries were at the work face, they accepted the presence of a bulldozer. The main period of feeding was 12.00-12.30 h when the tip closed at lunch time. (3) On most days, the gulls were feeding for 30-60 min and it was estimated that an individual, on average, fed for < 20 min per day. It is thought that most gulls did not feed elsewhere on days when they visited Coxhoe tip. (4) There was considerable variation and overlap between the times of arrival and departure of adults. The maximum numbers counted at any time during the day represented an average of c. 58% of the number of individuals that actually visited the tip on that day. This percentage varied from 46 to 79% in different months. (5) The pattern of arrival and departure of birds appeared to be determined mainly by the working day rather than the duration of daylight. (6) Most adult herring gulls did not visit the tip on consecutive days and the average number of days they were present in the 5 main working days in the week ranged from 1 4 to 2 1 days during the year. (7) Only 34% of the gulls that visited the tip during a week were present on any one working day. Few of these used other tips in the area on days they were not at the study site. (8) Work finished at 12.00 h on Saturdays and the numbers declined rapidly once the refuse was covered and work ceased. About 30% of the gulls seen on Saturday were present on the previous day and 10% were seen on Saturday for the first time in the week. (9) It is calculated that if 509 constituted the peak number of adult gulls at any one time during a day, 840 individuals visited during the day and 2745 during the week.