The pigeon guillemot breeds and sometimes roosts on rocky shores, cliffs, and islands close to shallow water.

This species feeds on small fish and marine invertebrates, mostly near the sea floor, that it catches by pursuit diving.

Pigeon guillemots are monogamous breeders, nesting in small colonies close to the shore.

The pigeon guillemot is considered to be a least concern species by the International Union for Conservation of Nature due to its large, stable population and wide range.

Threats to this bird include climate change, introduced mammalian predators, and oil spills.

Pallas noted in his description of this species that the common name for the related black guillemot was Greenland dove.

The trinomial epithet of the subspecies C. c. eureka is from the motto of the state of California, which is derived from the Greek heurēka, meaning "I have found it".

Both sexes are alike in appearance and mass, except for Californian birds where females were found to have larger bills than males.

The summer or breeding plumage of the adult is mostly dark brown with a black sheen, with a white wing patch broken by a brown-black wedge.

[9] Adults moult into their winter or non-breeding plumage between August and October, taking around a month to complete and leaving the bird unable to fly for around four weeks.

[8] The wings of the pigeon guillemot are shorter and rounder than other auks, reflecting greater adaptation towards diving than flying.

[8] The pigeon guillemot ranges across the Northern Pacific, from the Kuril Islands and the Kamchatka Peninsula in Siberia to coasts in western North America from Alaska to California.

Further south, birds banded in the Farallon Islands in central California have been recorded moving north, as far as Oregon and even British Columbia.

[8] This bird's breeding habitats are rocky shores, cliffs, and islands close to shallow water less than 50 m (160 ft) deep.

[14] On the other hand, larger auk species, tufted puffins and rhinoceros auklets, have been reported evicting pigeon guillemots from their nesting crevices.

Birds usually arrive in the colony in the morning, with counts decreasing after early afternoon, when high tide is.

Both parents are responsible for feeding the chicks, and bring single fish held in the bill throughout the day, but most frequently in the morning.

[8] Chicks fledge by leaving the colony and flying to sea, after which they are independent of their parents and receive no post-fledging care.

[8] The pigeon guillemot is a very vocal bird, particularly during the breeding season,[6] and makes several calls, some of which are paired with displays, to communicate with others of its kind.

[17] Low whistles are made by unpaired males attempting to attract a mate, and are deeper than hunch-whistles and involve less movement of the head.

[17] The pigeon guillemot forages by itself or in small groups, diving underwater for food, usually close to shore[20] and during the breeding season within 1 km (0.6 mi) of the colony.

[8] Smaller prey are probably consumed underwater, but larger organisms are brought to the surface to eat after capture.

It hangs upside down above the seafloor, probing with its head for prey and using its feet and wings to maintain position.

[13] Specialization in the prey taken by a pigeon guillemot when foraging for its chicks generally results in greater reproductive success, with a high-lipid diet allowing for more growth.

[20] The adult pigeon guillemot requires about 20% of its own weight, or 90 grams (3.2 oz) of food each day.

Species that prey on the nests include the northwestern crow, a common predator of both eggs and chicks, as well as glaucous-winged gulls, stoats and garter snakes.

[16] Adults are sometimes hunted by bald eagles, peregrine falcons, great horned owls[8] and northern goshawks.

[8] The pigeon guillemot is considered to be a least concern species by the International Union for Conservation of Nature.

[26] Climate change has a negative effect on this bird, and reproductive performance decreases with increased temperatures.