Description [edit]. The great cormorant is a large black bird, but there is a wide variation in size in the species wide range. Weight is reported to vary from 1.5 kg (3.3 lb) to 5.3 kg (12 lb).exel, Netherlands (2010). The great cormorant (Phalacrocorax carbo), known as the great black cormorant across the Northern Hemisphere, the black cormorant in Australia, the large cormorant in India and the black shag further south in New Zealand, is a widespread member of the cormorant family of seabirds.