- Measure 8–9 inches (20–23 cm); a dark, stocky, robin-sized seabird
- Slate-gray above, lighter gray below, white belly
- Eyes dark brown during first year, lightening to white in breeding adults
- Stubby bill has white spot at base of each side of lower mandible
- No seasonal change in plumage
Open ocean. Nests on sea cliffs and isolated headlands.
One white egg, usually placed in a burrow but also in a cavity among rocks. Nests in colonies.
Breeds from Aleutians to central Baja California. Winters in waters off southern part of breeding range.
Weak croaking calls given at night.