This shag lives on Heard Island. Museum specimens of adults show white cheek plumage extending above the gape. A diet study found that benthic animals, especially polychaetes, were common prey for much of the island population. Clements 2025 includes nivalis as a subspecies of Imperial Shag.
In a museum comparison, adult nivalis specimens were the only taxon with white cheek plumage reaching above the gape. They also showed broad white on the neck and white patches on the wings among the compared specimens.
Analysis of regurgitated casts from three Heard Island summers found benthic animals, especially polychaetes, to be common prey for most of the population. Fish were commonly eaten only by the small breeding population at the island's western end; elsewhere, fish remains occurred in 22% of casts.
An extinction-risk assessment has not been added yet.