Population Changes of Double-Crested Cormorants (Phalacrocorax auritus) on Four Islands in the Beaver Archipelago and Assessment of Aerial Photogrpahy as a Means of Monitoring Nesting Population Size
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Authors
Western, Jessica L.
Issue Date
2002
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
Since the mid-1970's, the double-crested cormorant population in many areas has
been steadily increasing. Often, this increase in cormorant numbers has been blamed for a decrease in sport and commercial fish populations. Because of a recent decrease noted in several fish populations in the Beaver Archipelago, including smallmouth bass, brown bullheads, and rock bass, a five-year study has been undertaken in order to better understand the double-crested cormorant and its relationship with these fish populations. This study looked specifically at the change in the cormorant population on the individual islands of Pismire, Hat, Gull, and Grape since 1997. There were two main goals in this study: documenting and accounting for any changes in the nesting
population of cormorants on Grape Island, and assessing aerial photography as a means of counting the number of nesting cormorants.
By combining ground counts from 2002 with those from previous years, it was
found that there has been a decrease in the nesting cormorant populations on most
islands. It was also discovered that the most likely reason for the desertion of the Grape
colony was repeated harassment by coyotes crossing onto Grape from Hog Island.
Counts taken from aerial photographs were found to differ significantly from counts
taken on the ground, however, with some improvements, it is believed that aerial
photographs could still be an important tool in the monitoring of nesting cormorant
populations.
Description
v, 25 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.