Cormorant abundance, diet, and foraging habits in Arizona
In Arizona, USA, Double-crested Cormorants (Nannopterum auritum) primarily overwinter, whereas Neotropic Cormorants (N. brasilianum) are common residents year round. Concern exists that both species are increasing in numbers and may have a negative impact on fish populations. We collected data durin...
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| Format: | Article |
| Language: | English |
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Resilience Alliance
2022-09-01
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| Series: | Journal of Field Ornithology |
| Subjects: | |
| Online Access: | https://journal.afonet.org/vol93/iss3/art6/ |
| _version_ | 1828098000016113664 |
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| author | Larisa E. Harding Jacob I. Mesler |
| author_facet | Larisa E. Harding Jacob I. Mesler |
| author_sort | Larisa E. Harding |
| collection | DOAJ |
| description | In Arizona, USA, Double-crested Cormorants (Nannopterum auritum) primarily overwinter, whereas Neotropic Cormorants (N. brasilianum) are common residents year round. Concern exists that both species are increasing in numbers and may have a negative impact on fish populations. We collected data during January 2017–April 2019 to characterize cormorant numbers seasonally, describe their foraging patterns, and evaluate environmental factors associated with cormorant numbers at community fishing waters. With more than 100 trained volunteers, we surveyed water bodies across the state simultaneously once each quarter of the year during January 2017–March 2018. We also visited 36 community fishing waters and other locations to document cormorant foraging activities and to explore potential associations between environmental factors and the maximum number of cormorants counted at each site. We collected stomach contents from lethally sampled cormorants to examine size and species of consumed fish. Our seasonal counts showed the greatest cormorant numbers during the winter and spring, with larger concentrations in metropolitan areas and fewer birds at higher elevations. At community fishing waters, cormorants fed primarily on fish ≤12 cm long, though they did consume larger sport fish in reservoirs and along the Colorado River. At community fishing waters, cormorant numbers were positively associated with the number of artificial structures in/near the water’s edge and with the number of large trees within 200 meters of the water. To reduce cormorant numbers and their anticipated impacts, we recommend stocking larger, stout-bodied fish and removing woody vegetation close to shorelines while adding fully submerged structures to provide security cover for fish from cormorants. This study is unique and important in that it addresses cormorant populations located in the southwestern USA, an area that has not historically been viewed as waterbird habitat, and it presents an unbiased evaluation of cormorant foraging activities in desert areas manipulated by water. It also offers reasonable, non-lethal actions to reducing potential cormorant impacts on aquatic resources. |
| first_indexed | 2024-04-11T07:55:38Z |
| format | Article |
| id | doaj.art-31eaba70675c4db0afaa594898c26266 |
| institution | Directory Open Access Journal |
| issn | 1557-9263 |
| language | English |
| last_indexed | 2024-04-11T07:55:38Z |
| publishDate | 2022-09-01 |
| publisher | Resilience Alliance |
| record_format | Article |
| series | Journal of Field Ornithology |
| spelling | doaj.art-31eaba70675c4db0afaa594898c262662022-12-22T04:35:56ZengResilience AllianceJournal of Field Ornithology1557-92632022-09-019336141Cormorant abundance, diet, and foraging habits in ArizonaLarisa E. Harding0Jacob I. Mesler1Arizona Game and Fish DepartmentU.S. Fish and Wildlife ServiceIn Arizona, USA, Double-crested Cormorants (Nannopterum auritum) primarily overwinter, whereas Neotropic Cormorants (N. brasilianum) are common residents year round. Concern exists that both species are increasing in numbers and may have a negative impact on fish populations. We collected data during January 2017–April 2019 to characterize cormorant numbers seasonally, describe their foraging patterns, and evaluate environmental factors associated with cormorant numbers at community fishing waters. With more than 100 trained volunteers, we surveyed water bodies across the state simultaneously once each quarter of the year during January 2017–March 2018. We also visited 36 community fishing waters and other locations to document cormorant foraging activities and to explore potential associations between environmental factors and the maximum number of cormorants counted at each site. We collected stomach contents from lethally sampled cormorants to examine size and species of consumed fish. Our seasonal counts showed the greatest cormorant numbers during the winter and spring, with larger concentrations in metropolitan areas and fewer birds at higher elevations. At community fishing waters, cormorants fed primarily on fish ≤12 cm long, though they did consume larger sport fish in reservoirs and along the Colorado River. At community fishing waters, cormorant numbers were positively associated with the number of artificial structures in/near the water’s edge and with the number of large trees within 200 meters of the water. To reduce cormorant numbers and their anticipated impacts, we recommend stocking larger, stout-bodied fish and removing woody vegetation close to shorelines while adding fully submerged structures to provide security cover for fish from cormorants. This study is unique and important in that it addresses cormorant populations located in the southwestern USA, an area that has not historically been viewed as waterbird habitat, and it presents an unbiased evaluation of cormorant foraging activities in desert areas manipulated by water. It also offers reasonable, non-lethal actions to reducing potential cormorant impacts on aquatic resources.https://journal.afonet.org/vol93/iss3/art6/arizonacommunity fishingdouble-crested cormorantnannopterumneotropic cormorantphalacrocoraxpiscivorywaterbird |
| spellingShingle | Larisa E. Harding Jacob I. Mesler Cormorant abundance, diet, and foraging habits in Arizona Journal of Field Ornithology arizona community fishing double-crested cormorant nannopterum neotropic cormorant phalacrocorax piscivory waterbird |
| title | Cormorant abundance, diet, and foraging habits in Arizona |
| title_full | Cormorant abundance, diet, and foraging habits in Arizona |
| title_fullStr | Cormorant abundance, diet, and foraging habits in Arizona |
| title_full_unstemmed | Cormorant abundance, diet, and foraging habits in Arizona |
| title_short | Cormorant abundance, diet, and foraging habits in Arizona |
| title_sort | cormorant abundance diet and foraging habits in arizona |
| topic | arizona community fishing double-crested cormorant nannopterum neotropic cormorant phalacrocorax piscivory waterbird |
| url | https://journal.afonet.org/vol93/iss3/art6/ |
| work_keys_str_mv | AT larisaeharding cormorantabundancedietandforaginghabitsinarizona AT jacobimesler cormorantabundancedietandforaginghabitsinarizona |