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04 - Eye of the Cormorant
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The bright emerald eye of the Double-crested Cormorant (Phalacrocorax auritus) in breeding plumage is quite striking. These birds are found throughout the United States, breeding in the north and wintering in the south, although a non-migratory population also lives in Florida. The birds feed primarily on fish caught while swimming completely submerged underwater. In some areas of the Everglades where the birds hunt regularly, native fish are being replaced by exotics such as oscars and walking catfish (Clarias batrachus). Oscars are much larger than the native fish which could make things difficult for the cormorants and other birds that feed on them. If the oscars grow too large then the birds cannot swallow them whole and will be unable to feed efficiently. While this has not occurred so far, cormorants do often take a longer time to swallow both the oscars as well as the walking catfish. The catfish have spines in their fins which make it necessary to swallow the fish perfectly or else risk getting the fish lodged. Ultimately, this increase in handling time of the fish reduces the feeding efficiency of the cormorants.
Anhinga Trail, Everglades Natoinal Park, Florida.
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