The Auckland shag is a colonial nester, building sizeable nests of, among other items, grass, twigs and seaweed.

The Auckland shag lays three pale blue-green eggs in November–February.

The Auckland shag is considered Vulnerable by the IUCN due to its small population size and restricted global range.

Some taxonomic authorities, including the International Ornithologists' Union, place this species in the genus Leucocarbo.

The specific epithet of this bird commemorates the naturalist William Colenso.