Wilson's Storm-Petrel

Wilson's Storm-Petrel is a diminutive seabird, barely larger than a swallow, with sooty-black plumage set off by a bright white band across the rump. Despite its tiny size, it is thought to be one of the most numerous bird species on the planet, with a global population estimated in the tens of millions.

This species breeds on Antarctica and subantarctic islands and then undertakes an impressive migration into the Northern Hemisphere, where it can be seen far out at sea across much of the Atlantic, Pacific, and Indian Oceans outside the Southern Hemisphere summer.

Wilson's Storm-Petrel has a distinctive feeding technique, hovering low over the water and pattering its long, yellow-webbed feet across the surface as if walking on water, while picking tiny prey items from the surface film with its bill.

Key field marks

• Very small size, roughly swallow-sized
• Sooty-black plumage with a bold white band across the rump
• Yellow webbing visible on the feet, often seen when pattering on the water
• Square-ish tail, unlike the forked tail of some other storm-petrels

Similar species

• Leach's Storm-Petrel has a forked tail and a more erratic, bounding flight, versus the more direct, fluttering flight of Wilson's Storm-Petrel.
• European Storm-Petrel is even smaller with a white underwing bar and lacks the trailing-leg pattering behavior as prominently displayed by Wilson's.

Wilson's Storm-Petrel breeds on Antarctica, the Antarctic Peninsula, and numerous subantarctic islands, nesting in rock crevices and burrows. It is one of the most widely distributed seabirds in the world, foraging across all major oceans.

Outside the Southern Hemisphere breeding season, the species migrates extensively into the Northern Hemisphere, occurring regularly far offshore in the North Atlantic and other ocean basins during the boreal summer.

Voice

Wilson's Storm-Petrels are largely silent at sea, but give soft chattering and purring calls at night around nesting crevices during the breeding season.

Feeding

They feed on planktonic crustaceans, small fish, and squid, characteristically hovering just above the surface with wings raised and pattering their feet across the water while picking food items from the surface film.

Nesting and breeding

Pairs nest in rock crevices, burrows, or under boulders on Antarctic and subantarctic ground, visiting the colony only at night to avoid predators. A single egg is laid, and both parents share incubation duties over an extended period.