Manx Shearwater

Overview

The Manx Shearwater is a slender, long-winged seabird with sharply contrasting black-above, white-below plumage, well suited to its characteristic low, banking flight over the ocean surface. It nests in burrows on offshore islands, often in large, dense colonies.

Its flight style, alternating tilted glides that flash dark and light sides in quick succession, is reflected in feathers that show strong, clean contrast rather than mottling or barring.

Manx Shearwater feathers show a clean, high-contrast pattern typical of many shearwaters.

• Upperparts: Blackish-brown, fairly uniform without barring, on the crown, back, and upperwing.
• Underparts: Crisp white on the breast, belly, and underwing coverts, with a sharp line of demarcation from the dark upperparts rather than a gradual blend.
• Flight feathers: Primaries are dark blackish-brown and narrow, built for stiff, extended gliding.
• Compared to similar shearwaters: The clean black-and-white contrast, lack of a dark cap contrasting with a paler collar (as in Great Shearwater), and generally smaller, slimmer feather size help separate Manx from bulkier shearwater species.

Adults show blackish-brown upperparts and clean white underparts including the underwing linings, with a sharp border between the two color zones. Sexes look alike. Juveniles closely resemble adults with only subtle differences in feather freshness. The molt is completed largely in the non-breeding range, away from the demands of the nesting burrow.

Manx Shearwaters breed in burrows on grassy or turf-covered offshore islands, mainly around the northeastern Atlantic, and undertake long transatlantic migrations to wintering grounds off the coast of South America outside the breeding season. They are highly pelagic when not breeding, ranging over open ocean far from land.

This shearwater feeds by plunge-diving and pursuit-diving for small fish and marine invertebrates, often foraging in flocks and following schools of prey fish. Its low, banking flight close to the water surface, alternating brief glides on stiff wings, is a hallmark of the species. Nesting occurs in burrows visited only at night to avoid predators, with a single egg laid per season and a long fledging period for the chick. Calls are harsh, cackling notes given at night around breeding colonies.