The very deeply black North Pacific subspecies Uria lomvia arra is also called Pallas' murre after its describer.

The thick-billed murre was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae.

[2] Linnaeus specified the type locality as boreal Europe but this was restricted in 1921 to Greenland by the German orthithologist Ernst Hartert.

[8] Four subspecies are recognised:[5] Since the extinction of the great auk in the mid-19th century, the murres are the largest living members of the Alcidae.

They differ from the common murre in their thicker, shorter bill with white gape stripe and their darker head and back; the "bridled" morph is unknown in U. lomvia – a murre has either a white eye-stripe, or a white bill-stripe, or neither, but never both; it may be that this is character displacement, enabling individual birds to recognize conspecifics at a distance in the densely packed breeding colonies as the bridled morph is most common by far in North Atlantic colonies where both species of guillemots breed.

[14] The thick-billed murre is distributed across the polar and sub-polar regions of the Northern Hemisphere where four subspecies exist; one lives on the Atlantic and Arctic oceans of North America (U. l. lomvia), another on the Pacific coast of North America (U. l. arra), and two others that inhabit the Russian arctic (U. l. eleonorae and U.

[15][16] Thick-billed murres spend all of their lives at sea in waters which remain below 5°C,[17] except during the breeding season where they form dense colonies on cliffs.

[9] Before 1950, large numbers appeared on the North American Great Lakes in early winter, passing up the St. Lawrence River from the East coast.

[22][23] Due to the enormous amount of energy needed to take off in flight, adults can only provide one food item at a time to their chick.

[15] Offspring of inexperienced pairs grow more slowly than those of experienced breeders, possibly because they do not receive as much food from their parents.

[24] Older and experienced adults obtain the better nesting sites located in the center of the colony, while the inexperienced individuals are kept on the margins[15] where their young are more likely to be preyed upon.

[27][9] The strong and direct flight of murres, which is, for their body size, the most costly form of sustained locomotion of any animal, is a result of their short wingspan.

[16] Other fish such as capelin (Mallotus villosus) and Myoxocephalus spp., as well as other crustaceans, polychaetes, and a few molluscs, are found in their diet but in relatively low numbers.

[15][29] Although declines have been observed in many parts of their range,[15] the thick-billed murre is not a species of concern as the total population is estimated to contain between 15 and 20 million individuals worldwide.

[16] Egg harvesting and hunting of adult birds are major threats in Greenland, where populations fell steeply between the 1960s and 1980s.

[30] In the Barents Sea region, the species has declined locally, due to influences associated with polar stations in Russia.

Populations at the southern edge of their range switched from feeding on ice-associated Arctic cod to warmer-water capelin[34] as ice break-up became earlier.