Soil Analysis of Double-crested Cormorant (Phalacrocorax auritus)
Nesting Colonies in Michigan's Eastern Upper Peninsula
Kristina M. Kasik
College of Natural and Health Sciences
Lake Superior State University, Sault Ste. Marie, MI 49783
Abstract
The Double-crested Cormorant ( Phalacrocorax auritus ) is a colonial nesting bird common to the Great Lakes. It is both migratory and piscivorous, and since the 1970’s when the use of DDT was banned, the population has been increasing in the Great Lakes and other areas. Because of the increasing numbers, the cormorant has become a concern to those involved with both aquacultures and sport fisheries. This has lead to much research regarding the feeding habits of the cormorant, but very little has been directed at other ecological aspects of the cormorant. The purpose of this study is to determine if the
Double-crested Cormorants has a significant ecological impact on nesting islands in
Michigan’s eastern Upper Peninsula. This was accomplished by collecting and analyzing soils from nesting and non-nesting areas to obtain values for five nutrients, pH, and the percent of organic material in each soil. The germination and biomass of a native plant species was calculated for each of the soil samples using Canada wild rye ( Elymus canadensis ), a grass species native to the area. The results of the soil analysis for nutrients, pH, and percent organic supported the hypothesis that the cormorants do affect the soil composition of the islands used for nesting. Results for both germination and biomass using a paired t-test also supported this (P-value < 0.05). This suggests that cormorants do have an ecological impact on nesting islands. This project should serve a foundation for further research concerning ecological interactions of the Double-crested
Cormorant in the Great Lakes region.
References:
Adams Jr., R.J., R. Brewer, and G. A. McPeek. 1991. The atlas of breeding birds of
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Erwin, R. M. 1995. The ecology of cormorants: Some research needs and recommendations. Pages 240-246 in The Double-crested Cormorant: biology, conservation, and management (D. N. Nettleship and D. C. Duffy, Eds.) Colonial
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P. Ludwig. 1995. Double-crested Cormorants of the Great Lakes: Changes in population size, breeding distribution, and reproductive output between 1913 and 1991. Pages 48-59 in The Double-crested Cormorant: biology, conservation, and management (D. N.
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