Manx Shearwater

How to find it

You will need a boat, since the records come from pelagic trips rather than from shore. Go expecting other seabirds first and treat a Manx as a surprise. On the Caribbean side, a later pelagic trip turned up Cory's, Great, Audubon's and Manx Shearwaters together, which shows what deep water can hold. On the Pacific side, a trip from Cabuya produced a bird that several visiting and local birders documented. Scan low over the waves for a stiff-winged glider flashing dark then white, and check size and leg colour if it comes close.

How to recognise it

This is a small shearwater, about 34 cm long. Look for these marks:

Dark brown upperparts.

White underparts.

A white underwing with a dark border.

A white undertail.

Flesh-colored legs, if you get a close look.

In flight it holds its long wings straight out from the body, which gives a cross-shaped outline. As it banks over the water it flashes black above and white below, and that contrast is the first thing to catch the eye.

Behaviour and diet

It eats small fish, crustaceans and molluscs, which it catches by diving. In flight it alternates flapping with gliding. Elsewhere birds are often in large flocks, gliding on air currents close to the water surface.

The flight is a stiff-winged shearing glide, tilting from side to side just above the waves.

Where it lives

The Manx Shearwater is a pelagic bird that feeds over open ocean waters. It nests in burrows on small islands or cliffs in the North Atlantic, so none of that happens in Costa Rica.

Here it has been recorded in waters off the Caribbean coast and on the Pacific side, from a boat trip out of Cabuya at the southern tip of the Nicoya Peninsula. Deep Caribbean waters may be visited more often than the records show.

When to see it

The Caribbean-side record came from a pelagic trip in late December 2021. That is one sighting, not a pattern for the species.

Similar birds

Little Shearwater looks similar, but the Manx is larger and has flesh-colored legs. In Costa Rican Pacific waters, Galapagos Shearwater is the common small shearwater, and it is worth comparing with the Manx. One has been watched in flocks with Black Terns, flying in a flutter and glide style.

Names and lore in Costa Rica

In Costa Rica the Spanish name is Pardela Manx. Elsewhere it is called Pardela Pichoneta, a name that refers to the chicks, which people traditionally collected for food, and also Fardela Atlántica. The English name Manx comes from an old shift in wording: in the 17th century the bird was called the Manks puffin, and puffin was an old word for cured shearwater chicks.

Status and conservation

Costa Rica's official list (AOCR) marks the Manx Shearwater as a migrant (M), while globally it is Least Concern with a large population, about 95% of it in Europe.