A heron that feeds along rocky shores and estuaries. It occurs in dark gray and white plumage forms and lives along coasts.
Its plumage ranges from dark grey through intermediate forms to white. Breeding birds develop narrow plumes on the head, foreneck, and back.
It searches rock pools and estuaries for small fish and crabs. Feeding often follows the falling tide; sometimes it spreads its wings to shade water and draw prey within reach.
In New Zealand it nests in low, dark places such as rocky caverns and under old bridges, usually in September–December. Both parents incubate the two to three eggs and feed the chicks.
Dark-morph juveniles are pale smoky-grey, while white-morph juveniles are white.
An extinction-risk assessment has not been added yet.