Thick-billed Murre Identification Guide

Key Field Marks

• Size & shape: A large, heavy-bodied auk, 40–48 cm, with a thick neck, short pointed wings, and an upright penguin-like stance on land.
• Plumage: Blackish head, neck, and upperparts contrasting sharply with clean white underparts; in breeding plumage the dark hood extends down the throat and comes to a distinct point on the upper breast.
• Bill: Relatively short and notably thick, all-dark, with a thin pale (whitish) line running along the gape near the base of the bill — the single best mark separating this species from Common Murre.
• Behavior: Highly gregarious, nesting in dense colonies on narrow cliff ledges; dives to considerable depths pursuing fish and invertebrates, using wings to "fly" underwater.

Separating Thick-billed Murre from Common Murre

• Bill shape: Thick-billed Murre has a notably stouter, shorter bill with the pale gape-line stripe; Common Murre's bill is thinner and lacks this pale line.
• Hood border: Thick-billed Murre's dark hood dips to a sharp point on the breast; Common Murre shows a straighter, less pointed border between dark throat and white breast.
• "Bridled" morph: Some Common Murres show a white eye-ring with a thin white line trailing back from the eye (the bridled morph) — a pattern Thick-billed Murre never shows.
• Overall tone: Common Murre upperparts often look slightly browner, while Thick-billed Murre appears more solidly blackish.

Where and When to See One

• Range: Circumpolar in the high Arctic and subarctic, breeding on sea cliffs from Alaska and Arctic Canada across Greenland, Svalbard, and northern Russia.
• Habitat: Nests colonially on narrow, bare rock ledges of steep sea cliffs, laying a single pointed (pear-shaped) egg directly on rock, an adaptation that reduces the chance of it rolling off.
• Season: Present at colonies spring through late summer; winters at sea, sometimes moving as far south as the northern United States and southern Europe during irruptive winters.

Voice

• Colonies are noisy with harsh, growling and purring calls exchanged between mates and neighbors; largely silent away from the breeding cliffs and while at sea.