It is a sooty-black storm petrel with a white rump and a white band crossing the lower belly and extending up the midline of the belly.

Despite considerable research, only one nest had ever been found prior to 2003, that being on the Isla Chungungo, off the coast of Chile.

Another possible breeding site may be inland in the Atacama Desert; a mummified chick, verified by DNA analysis, has been found in a crevice here, and signs of former activities in various cavities, but no live bird has been seen despite searches at various times of the year.

It seems likely that there are some breeding colonies in Peru, because the bird is quite common off the coast out at sea.

The population around the Galápagos Islands seems to be a resident and likely to be breeding, but again, no nesting site is known.