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BiologyAs a marine bird, the diet of the Campbell Island shag consists of fish and marine invertebrates. They feed in large flocks, sometimes up to 2000 birds, fanning out in a line before diving for prey (2) (5). Pursuit-diving is the most common feeding method of the shag, whereby the bird dives from the surface and propels itself underwater using its powerful webbed feet (2). Shags, like penguins, are impressively agile at sea, but appear awkward on land (2) (5). The behaviour of shags has given rise to many Maori sayings; someone obviously poised to leave is compared to a shag ready for flight, and the dejected air of a sitting shag gave rise to the phrase, 'as miserable as a shag on a rock' (5). It nests on cliffs, on exposed rocky ledges, hollows, or in sea caves, either solitary or in colonies of up to 150 nests (2) (4). Sometimes these colonies are mixed with gulls and terns (2). It is thought that the breeding season starts in August or September, and lasts until December (2), during which time two pale blue eggs are laid in a nest made mostly of tussock grass, with other plant matter and debris (2) (5). The oldest Campbell Island shag known lived for 13 years (4).