Wilson's Storm-Petrel

How to find it

Plan on a boat trip offshore, since the species is at sea except in big storms. Seabird watching from boats in Costa Rica is fairly new, and local birders around Cabuya and Cabo Blanco on the Nicoya Peninsula, and in Bahía Herradura, are leading it. Pelagic trips from Cabuya have been run by a local guide on fishing boats. For a short, easy taste, the Puntarenas to Paquera ferry across the Gulf of Nicoya makes storm-petrels possible, though none are guaranteed. At a distance, judge birds by flight style before plumage.

How to recognise it

Look for a tiny dark brown seabird, about 16 to 18.5 cm long, with blackish brown plumage.

The marks, in plain parallel phrases:

- a broad white band wrapping around the rump onto the undertail

- white lower flanks

- a pale, diffuse band across the upper wing coverts

- long legs

- a square-ended tail

- feet reaching about to the tail tip in flight

Adults have yellow webbing between the toes, a detail that is hard to catch over moving water. Young birds have paler-edged belly feathers.

Behaviour and diet

It flies low over the sea with a swallow-like, gliding flight. It hovers and pats the water with its feet while picking tiny food from the surface, facing into the wind and grabbing prey with its bill.

It is very social and often follows ships and fishing boats. That habit helps a boat-based birder, because a trailing bird may stay close enough to study its flight and marks.

Where it lives

Away from its southern breeding grounds, Wilson's Storm-Petrel lives strictly at sea. It comes near land mainly during big storms.

In Costa Rica, most older oceanic records come from the Pacific side, which seabirds visit on migration or during tropical storms. Offshore trips on that coast have recorded seabirds up to 380 km from shore, across northern, central and southern waters.

When to see it

A study of Pacific seabird trips off Costa Rica (2006 to 2010) found it most often on August and September trips. Older records fall in April, May, June and July off Playas del Coco, and a tour company list mentions good numbers from April to August.

Similar birds

It is often mistaken for Leach's or Band-rumped Storm-Petrels, but Wilson's has a more rounded band on the tail. Compared with the European Storm-Petrel, it has a pale band on top of the wing and no pale stripe under the wing, and its toes show beyond the tail. Elliot's Storm-Petrel, a long-shot for southern Central America, has a clear white patch on the belly. Off Playas del Coco, Black Storm-Petrels were told from Wilson's by a nighthawk-like flight and a rump that is white with a dark center streak or mostly dark with grey sides.

Names and lore in Costa Rica

The Costa Rican Spanish name is Paiño de Wilson. Other Spanish names include Paíño común, Pamperito de Wilson (also used in the Caribbean and Cuba) and Golondrina de mar (Chile).

Status and conservation

The official Costa Rican bird list classes Wilson's Storm-Petrel as a migrant (M) with the SC tag, and the world population, about 8 to 20 million birds (2022 estimate), is thought stable.

Photography tips

At a distance, judge storm-petrels by flight style before plumage: Wilson's flutters and patters across the water surface. Birds that follow fishing boats may stay close enough for a study of the rump and wing band.