Black-capped Petrel

How to find it

Be realistic: it is hard to find from shore, and Costa Rica has no known site where birders can see it. Costa Rican seabird records are mostly from the Pacific side, and this is not a Pacific bird. The nearest regular area is the southwestern Caribbean. Birders usually see it from boats in the Gulf Stream off Cape Hatteras, North Carolina, where it is common at sea, and that is the practical place to look. One ship survey in the Caribbean noted that birds were not attracted by chum, and the ship did not turn toward birds it saw.

How to recognise it

This is a large gadfly petrel, about 40 cm long, with a wingspan of about 94 cm. Look for these marks:

Blackish-brown upperparts.

White underparts, with a black leading edge and black tips on the underwings.

A dark cap running to the eye and nape, forming a partial collar on the upper breast.

A white forehead and a big white rump patch.

There is a dark-faced form and a light-faced form, so the amount of dark on the face can vary. Cornell calls it a 'flying field mark', which makes it one of the easier petrels to identify. These descriptions are for the species in general, not only for the single Costa Rican bird.

Behaviour and diet

The flight is high, erratic and deeply undulating, on steady wings. Over open ocean it is a fast flier with deceptively slow wingbeats, long glides and high arcs. It feeds over deep water along the edges of upwelling currents and is often seen in mixed-species flocks, loosely joining shearwaters and terns. It takes food such as squid from the sea surface. Nesting adults visit their mountain burrows only after dark, often on moonless nights. These habits describe the species across its range, not Costa Rican observations.

Where it lives

Away from its breeding grounds this petrel is almost entirely pelagic, living over open ocean. It comes to land only to nest, in burrows in montane forest at roughly 1,500 to 2,000 m on Caribbean islands. Its only known nesting area today is on the island of Hispaniola. Costa Rica has no breeding colony. In the Caribbean Sea it has been found from the central Caribbean south to coastal waters off Panama, Colombia and Venezuela, and the single Costa Rican bird was seen off the Caribbean coast.

When to see it

The one Costa Rican sighting dates to 14 August 1953, during a hurricane. In the southern Caribbean the petrels have been recorded only when coastal upwelling is active.

Similar birds

The Great Shearwater is the bird most often mistaken for it. The shearwater has longer, straighter wings, a thinner bill, a dark cap reaching the bill base and only a little white at the tail base, while the petrel has a white forehead and a big white rump. The Bermuda Petrel is smaller and slimmer, with a narrow white band on the rump and a dusky hood, but it is not a Costa Rican bird. A broad white rump reaching onto the tail points to Black-capped.

Names and lore in Costa Rica

Costa Ricans use the AOCR name Petrel Gorrinegro. Elsewhere in the Spanish-speaking world Cuba says Pájaro de la Bruja (witch's bird), the Dominican Republic says Diablotín, and Colombia and Spain say Petrel Antillano. Diablotín means 'little devil', from the eerie night calls at the nesting mountains, which locals linked with evil spirits.

Status and conservation

It is on the AOCR list as A-SC, a very rare vagrant in Costa Rica, and worldwide it is listed as Endangered.

Photography tips

Beginners should know it is hard to find from shore. One ship survey in the Caribbean noted that birds were not attracted by chum, and the ship did not turn toward birds it saw, so a steady boat and patience matter more than bait.