[3] The most similar species within its range is the Bermuda petrel, which is smaller and has a narrower white rump patch and an extensive gray cowl.

The black-capped petrel is nocturnal on its breeding grounds, possibly to avoid predation by gulls, hawks or crows.

The birds that visit these waters during the breeding season either represent non-breeders or are making long foraging trips away from the nest.

The black-capped petrel is almost strictly pelagic away from the breeding grounds and is known to join loose flocks with other seabirds such as shearwaters and terns.

[11] Most of the threats facing the black-capped petrel are on its nesting grounds, where causes for its demise include habitat loss, introduced predators, and direct harvesting by humans.

Human predation appears to have become more limited in scope than in historic times, due in part to the species' current scarcity.

Deforestation from wildfires and direct human use have likely decreased the amount of suitable nesting habitat available to the black-capped petrel.

Current conservation plans for the petrel largely involve preserving forest cover around known nesting areas as well as monitoring and searching for burrows.