Any of the 26–30 species of water birds, constituting the family Phalacrocoracidae, that dive for and feed on fish, mainly those of little value to humans. In the Orient and elsewhere, these glossy black underwater swimmers have been tamed for fishing. Their guano is valued as a fertilizer. Cormorants live on seacoasts, lakes, and some rivers, nesting on cliffs or in bushes or trees. They have a long, hook-tipped bill, patches of bare skin on the face, and a small throat pouch (gular sac). The most widespread species is the common, or great, cormorant (Phalacrocorax carbo), which grows up to 40 in. (100 cm) long and breeds from eastern Canada to Iceland, across Eurasia to Australia and New Zealand, and in parts of Africa.
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Shag may refer to one of the following: