Australia has five species of cormorants or shags: two large and three small. Unsurprisingly the Great Cormorant Phalacrocorax carbo is the largest. Like the darter it is an occasional but distinctive visitor to the wetlands.
The great cormorant is the size of a small goose. It is a jet black bird with a neutral beak and yellow skin on and around its face. Young birds are dull brown, while breeding birds are glossy black with white streaks on their necks, a white patch on their faces and one on their lower flank. Like all cormorants it has a long bill that is hooked at the end and large webbed feet held so far to the rear of the body that it is forced to stand vertically when on land. There it waddles clumsily but in water is extremely agile and graceful. Its voice is a deep croak or cough.
The great cormorant has several common names in addition to this one, including black shag, black cormorant and big black cormorant. As a species it is found throughout much of Australia and the rest of the world.
Like all its family the great cormorant swims with its body partly submerged. It feathers are sparse and not waterproof, so need to be hung out to dry after it comes out of the water. It will often stand or perch with its wings open for long periods. This posture apparently may also assist in digestion.
Great cormorants are highly nomadic and can fly great distances looking for large bodies of water, but will settle for larger farm dams and deep pools. Although often seen singly, great cormorants will actively form large groups to cooperatively hunt larger schools of fish. It is quite a sociable bird and is often seen in the company of other species. In the breeding season it can form communal nesting sites with tens of thousands of other great cormorants, especially during major inland flooding events.
The great cormorant is primarily a hunter of fish, but will readily eat other pond life, such as frogs, young turtles, large water insects, yabbies and prawns. Some farmers and fishermen loathe cormorants for the fact that they readily devour most if not all of the young fish that they stock in their dams and lakes for recreational purposes. Unfortunately the same fishermen have little regard for the damage they do to aquatic ecosystems by unleashing what are mainly introduced predators (such as trout and salmon) onto native fish and water creatures. Nonetheless, it is possible to have your fish and cormorants too. When artificial dams and lakes are merely basins containing water with little or no shore vegetation, fish become easy marks for hunting cormorants. By allowing floating and shoreline plants to colonise and providing or not removing log jumbles and overhanging trees (preferably native trees and definitely not invasive willows, poplars or alders), fish can gain protection from cormorants.