The Wilson's Storm-Petrel is a small bird, 16–18.5 cm in length with a 38–42 cm wingspan.
It is essentially dark brown in all plumages, except for the white rump and flanks.
Like most other storm-petrels it flies low over the sea's surface and has the habit of pattering on the water surface as it picks planktonic food items from the ocean surface.
Their unique fluttering and hovering flight is achieved often with their wings held high.

Cape Cod, Massachusetts, USA, 11 August 2017