Summary

Return to Conservation Biology Research on Birds

Goodermote, D. L. 1984. A survey of nesting herring gulls along the north shore of Lake Superior from Knife river to the Pigeon river, during the period 1977-1984. Final report submitted to the Minnesota Department of Natural Resources. 71 pp.

Summary:

The objectives of this study were: 1) inventory all breeding colonies of Herring Gulls, and 2) analyze year-to-year changes taking place on individual nesting sites by development of population models. Fifteen sites were chosen to be monitored over four years. To validate the accuracy of the monitoring system, a complete survey of all North Shore sites was conducted during the 1984 breeding season. A June 1st storm resulted in large numbers of dead chicks. Cause of death believed to be a result of the cold, hard driving rain, which accompanied the storm, and the high waves which must have rolled over some of the nesting sites. This storm may have a drastic effect on the number of three year olds returning in the 1983 nesting season. In 1982 the nests throughout the North Shore seemed to have fewer eggs than in past years, a large number of eggs appeared to be smaller, as well. In 1983 the total number of active nests on the survey was down 4.15%. Presence of large numbers of empty nests late in May, when incubation was almost at an end, suggests that birds made an attempt to nest but for some reason did not lay eggs. Adult birds were in poor physical condition which may have been caused by poor food conditions on the wintering area or may have been a direct result of the extremely poor smelt run this spring. In 1984 the western half of the study area increased 41% above 1978 level. The increase was not constant. The eastern half of the study area increased 13% above the 1978 level. A sizable drop in the number of nesting birds in 1983 thought to be the result of the 1980 storm which created a shortage of 3 year old replacements. Dump locations, method of waste treatment, and changes that have taken place regarding dumping have not been documented but are believed to impact the nesting biology of the herring gulls because of their dependency on human dumping areas. The number of nesting birds within a Herring Gull colony appears to fluctuate regularly. Herring Gulls require a number of years to reach breeding age, and it was thought these peaks and lows occurred in response to a change in the survival of young birds in prior years. It is believed that the year-to- year fluctuations have very little to do with changes in the environment.

Full document (1698 KB) This is a PDF file. You will need Adobe Acrobat Reader to download it.