The Thick-billed Murre (Uria lomvia) is a stout, black-and-white seabird in the auk family (Alcidae), known for its heavy head, short stout bill, and ability to dive over 100 meters for prey. It breeds in dense colonies on narrow sea cliff ledges and winters in open ocean waters, where it is a far more agile swimmer than flyer.
Learn to identify
Adult Thick-billed Murre in summer plumage at a breeding cliff, Alkefjellet, Svalbard.
Learning lesson · openly licensed photographs, labelled by BirdBot; labels checked against the cited sources and approved by AI
Like a Common Murre, but check the bill. White gape stripe: a white line on a thicker, shorter bill. Blackish head: darker than a Common Murre's. Pointed white chest: in summer the white may run up in a point. Black back and wings: blacker than Common Murre, hard to judge alone. Look for the white gape stripe on a thicker bill. Winter birds have a whiter lower face.
Winter birds have a whiter lower face.
Sources: Wikipedia: Thick-billed murre (revision 1382491689) · Audubon Guide to North American Birds: Thick-billed Murre
Photo: Jerzy Strzelecki, CC BY-SA 3.0, via Wikimedia Commons; labels added by BirdBot.
Thick-billed Murres are immediately recognizable by their robust build and upright, penguin-like stance, a posture resulting from their webbed feet being set far back on their bodies. Adults display a sharp contrast of black feathers on the head, back, and wings, and white feathers on the breast and underside. The bill is spear-shaped and grey-black, featuring a distinct white line running along the sides of the upper mandible. This white line is a key diagnostic feature: it is typically more prominent and continuous in breeding plumage, while the neck and face become a noticeably paler grey during the non-breeding (winter) season.
Comparison with Common Murre: The most critical field cue for separating this species from the similar Common Murre (Uria aalge) is the bill structure. The Thick-billed Murre has a heavier head and neck and a noticeably shorter, stouter bill. Additionally, the Thick-billed Murre's back appears blacker, and it lacks the brown flank streaking typically found on Common Murres. Juveniles resemble adults in plumage but possess a smaller, more slender bill.
Thick-billed Murres are marine birds that remain along sea coasts as far offshore as the continental shelf edge. They breed on the cliffs of high and low Arctic (locally subarctic) Holarctic coasts. During the non-breeding season, they are most often found in large flocks out to sea in the open ocean, though vagrants blown inland may occasionally appear in bays, estuaries, or reservoirs. They are generally found in greater numbers on islands rather than on mainland coasts.
Thick-billed Murres are primarily aquatic, foraging in waters colder than 8°C. They are notable as one of the deepest underwater divers, reaching depths of more than 100 meters (330 feet) in pursuit of prey. While they can fly at speeds of up to 75 mph once airborne, this figure is a single-source estimate from the Animal Diversity Web and should be treated as a general approximation rather than a verified maximum. They swim far better than they fly due to their awkward takeoff.
Foraging patterns vary by prey type and habitat. As generalist marine predators, they actively pursue schooling mid-water pelagic prey. In contrast, they spend more time but less energy searching for benthic prey, gliding slowly along the sea bottom to probe sediments or rocks. Diet composition also shifts with location: at offshore ice edges, they feed in the water column and under landfast ice, while at coastal ice edges, they forage at the ice undersurface, on the sea bottom, and in the water column.
During the breeding season, Thick-billed Murres form large, dense, and noisy colonies on narrow cliff ledges. The birds stand side by side, creating a tight-knit nesting habitat that helps protect them and their chicks from aerial predators. They are generally active during the day.
Thick-billed Murres begin breeding between five to six years of age. Females lay a single egg with a thick, heavy shell, often greenish to pinkish in hue with mottling patterns. The egg is pear-shaped, which prevents it from rolling when jostled on the bare ledge. Females do not build nests but arrange pebbles and debris close to the egg, securing it in place with feces to prevent it from rolling off the cliff.
Both parents incubate the egg, taking shifts of 12 to 24 hours over an average 33-day period. After hatching, both parents feed the nestling, mainly fish, for approximately 15 to 30 days. The chick usually fledges at about 21 days old. After the female departs for the sea, the male parent stays to care for the chick for 4 to 8 weeks. Upon fledging, chicks swim nearly 1,000 kilometers (620 miles) accompanied by their male parent in the first leg of the journey to their wintering grounds (a single-source estimate from ADW).
Adult Thick-billed Murres emit lower-pitched, gruff calls that resemble a laughing “ha ha ha” or a prolonged growl. There is individual variation in these calls based on pitch, duration, and syllable count, which may allow for individual recognition. Chicks produce flute-like sounds, including a rapidly frequency-modulated departure call used to communicate with the male parent shortly before, during, and after they leave the colony as fledglings.
The Thick-billed Murre is classified as Least Concern (LC) in the AviList v2026 checklist. While the global population is large, it faces threats from oil spills, gill-netting, and predation by gulls. Specific population estimates and threat severity assessments are not provided in the current verified sources.
When observing Thick-billed Murres, it is essential to maintain a significant distance, especially during the breeding season. Their colonies are dense and sensitive to disturbance; approaching too closely can cause stress, egg loss, or abandonment of nests. Use binoculars or a telephoto lens to observe their upright posture and deep diving behavior from a safe vantage point on rocky coastlines or offshore waters.
Field Identification Cues: Look for the distinct white line running along the sides of the upper mandible of the bill. Note the bird's posture during takeoff; due to their feet being set far back, they have an awkward, penguin-like launch that contrasts with their agile swimming. In winter, check for the paler grey neck and face to distinguish them from the darker breeding plumage.
If you encounter a vagrant in a bay or estuary, observe quietly and report the sighting to local birding groups to aid in tracking unusual movements.
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