Medium-sized cormorant, smaller and slighter than Great, with thinner head, neck and bill; told from Little by larger size, longer, thinner neck, bill, and shape of head – oval rather than angular; no crest; breeding plumage black with bronze-green sheen, white ear-tuft, white flecked-feathers on neck, blackish gular pouch; non-breeding shows browner plumage, no ear-tuft or white plumes, yellower gular pouch; immature whiter below; gregarious; often in flocks; will fish together  with Little; colonial nester.