It is highly coastal, rarely foraging far from shore, although sometimes feeds in the large and brackish Te Whanga Lagoon.

The species is threatened by introduced predators, disturbance at its breeding colonies and habitat loss.

[8] "Chatham Islands shag" has been designated as the official common name for the species by the IOC.

[9] An adult Chatham Islands shag is 63 cm (25 in) in length and weighs around 1,790–2,400 g (63–85 oz).

[4] It is a large pied shag with a white throat, breast, belly and patches on the scapulars of the wings, and black or black-brown elsewhere.

Adults have a red gular sac and orange-red caruncles on the face and the gape of the mouth.

The bill is dark grey, with a bright red mouth, and the legs and feet are dull pink.

[10] The species is endemic to the Chatham Islands, an archipelago around 700 km (430 mi) to the east of New Zealand.

In the Chathams it is an inshore species, rarely going more than a few kilometres away from shore, and it is more commonly found in sheltered water such as bays and inlets.

[12] Like all cormorants, the Chatham Islands shag is a pursuit-diver, propelling itself underwater with its feet and returning to the surface to consume small prey caught in its bill.

[13] The specific diet of the Chatham Islands shag is poorly known,[4] but is dominated by fish, including opalfish, flatfish and bullies, as well as cephalopods such as octopuses, squid and cuttlefish.

Colonies on the main islands are also vulnerable to introduced predators such as weka, feral cats and possums.