Birds
Chatham Shag
Leucocarbo onslowi · also called Chatham Island shag
Confined entirely to a single remote South Pacific island group, a Chatham shag ranks among the rarer blue-eyed shags, its small population leaving it exposed to any localised threat that might strike its one and only home.
Overview
The Chatham shag, Leucocarbo onslowi, is an Endangered seabird native to ocean and coastal habitat found only on the Chatham Islands, a remote outpost of New Zealand in the South Pacific. Its single-island endemism, comparatively small population, and heightened vulnerability to localised threats make it one of the more conservation-critical blue-eyed shag species found anywhere in the region.
Rarity concentrated on one small island
With every Chatham shag confined to the same small island group, the species carries a level of risk shared by few other seabirds, where a single bad season or localised disaster could meaningfully threaten its entire world population at once.
Status
Endangered, with populations remaining small and confined entirely to the Chatham Islands, and numbers considered to be declining given the species’ extremely restricted range.
Chatham Shag: common questions
Where does the Chatham shag breed?
This species breeds only on the Chatham Islands, a remote New Zealand island group in the South Pacific, making it entirely endemic to that one location.
Why is the Chatham shag called a blue-eyed shag?
This species has a vivid ring of bare, blue-coloured skin around each eye, a feature shared with several closely related shag species collectively nicknamed blue-eyed shags.
Why is the Chatham shag considered Endangered?
This species faces a heightened extinction risk because its entire population is confined to a single small island group, leaving it exposed to any localised storm, disease outbreak, or disturbance.
How rare is the Chatham shag compared with other blue-eyed shags?
This species is considered one of the rarer blue-eyed shag species, with a total population smaller than many of its close relatives found elsewhere across the subantarctic islands.