Publication Date

1973

Document Type

Dissertation/Thesis

First Advisor

Southern, William E.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences

LCSH

Birds--Food; Ring-billed gull

Abstract

Regurgitated Ring-billed Gull food samples were collected in 1964 and 1971 at three Michigan breeding colonies, two on Lake Huron and one on Lake Michigan. The preliminary study (1964 samples) in­dicated the gulls consume a tremendous diversity of insects as well as several species of fish. The more comprehensive phase of the study (1971 samples) indicated fish to comprise 76% of the total diet volume (6l% frequency of occurrence), insects - 22% volume (64% frequency) and earthworms - 1% volume (5% frequency). Volumetrically, the most important fish were smelt, alewives and stickleback, named in the order of their importance. The primary insects consumed were cicadas, mayflies, midges and beetles. From May through July, fish consumption increased while the amount of insects eaten was greatest in June. Earthworms were eaten primarily in May. Comparing island and mainland colonies, fish consumption was greater for the island ­dwelling birds while insects and earthworms were more voluminous in the mainland birds' diet. The amount of smelt, alewives and stickle­back eaten varied as the season progressed; these changes appeared to be related to the time of spawning for the various fish. Insects and/or earthworms appeared in the birds' diet throughout most of the season, indicating considerable terrestrial feeding effort by the birds. In previous reports of Great Lakes Ring-billed Gull foods, alewives were said to be the most abundant fish in the diet but this study does not confirm that contention. Garbage appears to be of very little importance in the ring-bill diet. Population dynamics and interspecific competition are discussed as they relate to food habits. Also discussed are various aspects of adult and chick feeding behavior.

Comments

Includes bibliographical references (pages 59-61)

Extent

63 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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