Species Highlight: Double-crested Cormorant
On October 23 I spotted three Double-crested Cormorants (Phalacrocorax auritus) resting with about 75 Herring Gulls on a concrete structure just off the Lake Michigan shoreline. I used Cornell Lab's Merlin Bird ID for the identification as I had never observed them before. After a bit of research I came to learn that these birds have a very interesting history. What's more, they seem to have a pretty arduous future.
But not everyone is thrilled by their comeback. The U.S. Fish and Wildlife Service issues depredation permits for the purpose of culling the species in the United States. Their 2017 Environmental Assessment determined that up to 51,571 Double-crested Cormorants can be taken every year (USFWS 2019). Last year, Ontario proposed a cormorant hunting season which would allow a single hunter to take up to 50 birds in a single day!
Most permits are not issued on the basis of recreation or subsistence; many request them for the purpose of reducing a "nuisance" species. Cormorants are known to have significant impacts on fisheries, vegetation, and other wildlife. Many support the effort to reduce their populations, but others question whether or not we'll push them towards another decline. Some note that Double-crested Cormorants are beneficial co-nesters of other species like Herring and Ring-Billed Gulls and that their positive impacts should also be considered (Wyman et al. 2017).
Where do you stand? Post your thoughts in the comments below!
Double-crested Cormorants are one of 38 cormorant species in the world and one of six found in North America (USFWS 2016). Don't let their relatively small size fool you - their average wing span is about 4.5 feet (USFWS 2016). Their diet consists primarily of fish so they are typically found near shorelines of oceans, lakes, rivers, and other water bodies.
The Great Lakes populations (spanning United States and Canada) had only 598 nesting pairs in 1977 (Wyman et al. 2017). This prompted various conservation and protection efforts and bans on pesticides like organochlorine (OC) - highly toxic, slowly degrading, and bioaccumulative compounds that were once widely used in agriculture and chemical industries in North America (Jayaraj et al. 2016). Double-crested Cormorants are protected by the Migratory Bird Treaty Act which, in theory, prevents them from being harmed or killed. In recent years, their populations have been booming.
Double-crested Cormorants (based on coloring, these are likely juveniles)
The Great Lakes populations (spanning United States and Canada) had only 598 nesting pairs in 1977 (Wyman et al. 2017). This prompted various conservation and protection efforts and bans on pesticides like organochlorine (OC) - highly toxic, slowly degrading, and bioaccumulative compounds that were once widely used in agriculture and chemical industries in North America (Jayaraj et al. 2016). Double-crested Cormorants are protected by the Migratory Bird Treaty Act which, in theory, prevents them from being harmed or killed. In recent years, their populations have been booming.
For more information, visit https://birdsna.org/Species-Account/bna/species/doccor/introduction.
But not everyone is thrilled by their comeback. The U.S. Fish and Wildlife Service issues depredation permits for the purpose of culling the species in the United States. Their 2017 Environmental Assessment determined that up to 51,571 Double-crested Cormorants can be taken every year (USFWS 2019). Last year, Ontario proposed a cormorant hunting season which would allow a single hunter to take up to 50 birds in a single day!
Most permits are not issued on the basis of recreation or subsistence; many request them for the purpose of reducing a "nuisance" species. Cormorants are known to have significant impacts on fisheries, vegetation, and other wildlife. Many support the effort to reduce their populations, but others question whether or not we'll push them towards another decline. Some note that Double-crested Cormorants are beneficial co-nesters of other species like Herring and Ring-Billed Gulls and that their positive impacts should also be considered (Wyman et al. 2017).
Where do you stand? Post your thoughts in the comments below!
Resources
- Jayaraj, R., Megha, P., & Sreedev, P. (2016, December). Organochlorine pesticides, their toxic effects on living organisms and their fate in the environment. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5464684/.
- U.S. Fish & Wildlife Service. (2016, June 29). Double-crested cormorants. Retrieved from https://www.fws.gov/southeast/faq/double-crested-cormorants/.
- U.S. Fish and Wildlife Service. (2019, August 1). Reports & Publications. Retrieved from https://www.fws.gov/birds/management/managed-species/double-crested-cormorants.php.
- U.S. Fish and Wildlife Service: Division of Migratory Bird Management. (2017). Environmental Assessment for Issuing Depredation Permits for Double-crested Cormorant Management. U.S. Fish and Wildlife Service. Retrieved from https://www.fws.gov/migratorybirds/pdf/management/double-crested-cormorants/CormorantEA.pdf
- Wyman, K. E., Wires, L. R., & Cuthbert, F. J. (2017). Great lakes double‐crested cormorant management affects co‐nester colony growth. The Journal of Wildlife Management, 82(1), 93–102. doi: 10.1002/jwmg.21343
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