| Abstract: | The piscivorous nature of the Double-crested Cormorant (Phalacrocorax auritus) is well documented. However, many researchers who have used regurgitated pellets to describe the diet of cormorants report that invertebrates compose a small but consistent portion of the diet. We examined the hypothesis that invertebrates found in pellets are primarily the result of secondary consumption. We used odds ratio analysis to examine associations in 2,846 individual pellets between the presence of specific invertebrate prey and the presence of fish species known to consume those invertebrate taxa. Significant (P < 0.05) relationships occurred between gastropods and pumpkinseed (Lepomis gibbosus) and ictalurids, and between decapods and rock bass (Ambloplites rupestris) and smallmouth bass (Micropterus dolomieu). Significant (P < 0.05) relationships were also found between pelecypods and pumpkinseed and ictalurids. We suggest that the invertebrate prey we observed in pellets were present in the digestive tracts of fish that were consumed by Double-crested Cormorants and hence represent secondary consumption by cormorants. We conclude that consumption of invertebrates by Double-crested Cormorants may be overestimated in the literature in instances where the diet was described using pellets. |
| Genre: | Article |
| ProdID: | 70019272 |
| Citation Author: | Johnson, J. H.; Ross, R. M.; Smith, D. R. |
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| Citation End Page: | 551 |
| Citation Issue: | 3 |
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| Citation Language: | English |
| Citation Larger Work Title: | Waterbirds |
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| Citation Number Of Pages: | 5 |
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| Citation Search Results Text: | Evidence of secondary consumption of invertebrate prey by Double-crested Cormorants; 1997; Article; Journal; Waterbirds; Johnson, J. H.; Ross, R. M.; Smith, D. R. |
| Citation Start Page: | 547 |
| Citation Volume: | 20 |
| Citation Year: | 1997 |
| Type: | citation/reference |
| Text: | Evidence of secondary consumption of invertebrate prey by Double-crested Cormorants; 1997; Article; Journal; Waterbirds; Johnson, J. H.; Ross, R. M.; Smith, D. R. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 1997 00:00 -0600 |
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