During the 1977-1985 period a colony of 80-120 Little Shags (Phalacrocorax melanoleucos brevirostris
) was studied at Hobson Bay, Auckland City. The breeding season of Little Shags was from August to March or April. Pied Shags (Phalacrocorax varius
), which joined the colony during the study period and have tended to displace the smaller species, have nested throughout the year. For both species highest numbers of nesting pairs were present in spring (October – November). Little Shags of the pied form constituted one-third of the colony and interbred freely with birds of the white-throated and smudgy plumages. Fledglings have either the pied or totally black plumage and both can occur within the same brood. Aspects of behaviour are described and a detailed account of the colony is given.