Common Murre Uria aalge Scientific name definitions

David G. Ainley, David N. Nettleship, and Anne E. Storey
Version: 2.0 — Published August 6, 2021


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Walking, Running, Hopping, Climbing, etc.

Shuffles on tarsi, sometimes aided by flapping wings. Climbs readily using toenails, aided by flapping wings. More agile than Thick-billed Murre (Uria lomvia; 211). Shares many osteological characteristics with Pinguinus and Alca, related to upright stature when on breeding ledges (292).


Owing to high wing-loading (184 Newtons/m2) and low aspect ratio (9.5), must flap wings rapidly and fly fast to stay aloft (293); one of the highest wing-loading of any living alcid (up to 2.06 g/cm2, n = 20), but well below threshold for flightlessness (2.5 g/cm2; 294, 204). One account describes its flight as follows: “Literally dives into the air from its nesting ledge” (38: 22).

Males have higher aspect ratio than females to support greater mass (23; see Measurements in Appendix 1). Speed measured roughly at 21.7 m/s (78 km/h; 295); 19.2 m/s (69 km/h; 296); and >16.8 m/s (60 km/h; 38). However, flight speed changes with wind speed and direction. Measured more precisely, as wind speeds change from 3 m/s to 12 m/s, ground speed changes as follows: tailwind, 20 to 25 m/s; cross wind, 21 to 19 m/s; headwind, 19 to 14 m/s (297). In strong winds, may glide just before landing on water. In light winds, lands abruptly, sometimes awkwardly; in high winds, may almost hover before landing at breeding site, its body twisting wildly as it seeks to place its feet appropriately (i.e., not on top of mate or chick).

Swimming and Diving

A wing-propelled pursuit diver. See Diet and Foraging: Feeding. Immediately after jumping from cliffs, chicks can dive for short periods to escape predators, but not well enough for foraging. The exact age when they begin to dive for food is unknown, but some time later chicks start diving and may supplement parental feedings (H. R. Carter and S. G. Sealy, unpublished data). Requires their primary feathers to have grown sufficiently long in order to dive effectively, which can take on the order of weeks after leaving the cliffs. Adults are incredibly adept as divers.


Preening, Head-Scratching, Stretching, Sunbathing, Bathing, Anting, etc.

Bathes and preens extensively while on water (178). In the colony, preens self and allopreens mate and neighbors (AES).

Sleeping, Roosting

Sleeps with or without head tucked into scapulars, on land or floating on sea. Roosts in large rafts on water; nonbreeders have roosting areas at colony periphery.

Daily Time Budget

Visitation of breeding sites for murres at high latitude is seasonal, breeding season only, but at lower latitudes such as central California and North Sea individuals are totally absent only during the post-breeding molt when they are flightless (27, 92). Winter visitation occurs regularly, but is episodic, and occurs only during the daylight hours. As the breeding season approaches, frequency of night time presence increases.

At colony during incubation and chick-brooding (e.g., Gannet Islands, Labrador), breeding birds averaged 17 h (range 1–38) incubating, and 4 h (range 1–14) and 12 h (range 7–20) brooding chicks during day and night shifts, respectively; remaining time mostly spent at sea (298). No differences, on average, in shift duration between sexes, though more females than males incubated/brooded at night in some colonies (298), but not in others (299). More time spent sleeping and preening during incubation than when brooding.

At sea, time spent by active breeders provisioning chicks, flying between colony and foraging area, diving in pursuit of prey, and sitting on sea-surface resting varies with environmental conditions, as does time spent at colony. Harding et al. (230, 300) found: (1) a strong positive non-linear relationship between food density and colony attendance during chick-rearing at low to medium food abundance, but no relationship through a range of high food densities; relationship was weaker during incubation; (2) that incubating birds only reduced colony attendance under extremely poor feeding conditions; and (3) that incubating birds spent more time attending breeding sites than provisioning birds. Although one parent is almost always with the egg or chick, if food availability is particularly poor, chicks are left alone, leading to breeding failures or even colony failures if inattention is widespread (e.g., Castle Rock, California; 232). Pairs spend more time co-attending in the colony when foraging conditions are better (in Alaskan, British, and Newfoundland colonies: 178, 301, 302, 230, 300, 303), allowing more time for them to loaf and/or negotiate parental duties (304).

Partitioning of time among nonbreeders or during nonbreeding season at sea little studied. During winter, spends very little time flying; rests at night often in special areas, moving to where foraging is productive during the day, when light is sufficient (216, 92; see Diet and Foraging: Feeding). Food availability more than day length determines amount of foraging during nonbreeding season (92). Time spent diving nearly doubles from early to late winter through spring, indicating that this period is particularly challenging (168, 92). Intensity of winter foraging is also related to change in telomere length in Thick-billed Murres: more intensive winter foraging was associated with a greater over-winter decrease in telomere length (285).

Agonistic Behavior

Physical Interactions

Fighting common, usually associated with territory or mate defense (38, 289, 305). Aggression level progresses: Bill-pointing, jabbing at opponent (especially its bill), locking of bills, beating with carpus of wing, and twisting to force rival from ledge. At highest-intensity jabbing, bill open with low-intensity gargling. Fights may occasionally continue for hours, ending with exhaustion and invariably head-shaking, possibly as an appeasement behavior. Frequency of all interactions, including fighting, increases throughout prelaying and decreases at egg-laying (AES).

Aggression level directly related to density, from zero among dispersed territory holders (>1 body length apart) to 0.02–0.10 encounters/bird/min (289). Average duration of encounters 4.5 s, with 40% involving physical contact. Incubating birds much less aggressive than off-duty individuals; pecked by incubating birds, trespassers retreat. Aggression high during prelaying, declining only to increase again at end of chick rearing.

Older subadults more likely than younger subadults to start and win fights, but younger birds more likely to be in fights; aggressiveness and competence in agonistic behavior likely of value in securing a high-quality breeding site (306).

Communicative Interactions

Active appeasement performed in response to attack as follows (289): (1) Side-Preening. Performed by incubating or brooding birds; also a few seconds after a bird alights in vicinity of others. (2) Stretch-Away, an in-out movement of neck. A passive display, performed more often by incubating than non-incubating birds, in response to bird(s) moving nearby; more frequent among densely packed birds. (3) Turn-Away; i.e., rotating body away; also can be passive. In addition, incubating neighbors engage in allopreening one another.

Mates allopreen each other during co-attendance. Breeding site reliefs are less likely to occur if the brooding murre allopreens less often, or starts later, than the returning bird (307), which suggests that allopreening by brooders signals readiness for an exchange.

Passive appeasement performed before any attack or aggression, signaling “please don't peck me.” In Post-landing Display, bird assumes a head-up-and-wings-out-and-up posture for an instant. If it advances, then it does so in Ritualized Walk, with head stretched upward and wings open (or not); when walking by a group, its head is down, wing(s) up.

Site ownership signaled by mutual bowing, between partners, and Post-landing Display. Increased aggression occurs in process of territory establishment, or re-establishment in the case of rock falls.

Territorial Behavior

No true nest; defends precise, individual space adequate in size for pair exchange while incubating egg and brooding chick; birds normally retain exactly same breeding site each year through life, with high site fidelity (>90% of returning birds, 308, 309, 310, 156, 311). Intruders and prospectors kept at pecking distance by aggressive Jabbing (see above).

At sea, often concentrated in rafts, but no exact individual distance or territory defended. Brooding murres in dense colonies can be in physical contact with several neighbors.

Sexual Behavior

Mating System and Operational Sex Ratio

Socially monogamous with equal sex ratio (312) and frequent extra-pair copulation behavior, but relatively low level of extra-pair paternity, at approximately 7–8% (313, 314).

Courtship, Copulation, and Pair Bond

Greeting ceremony, occurring throughout the breeding season, has many elements similar to aggression; occurs 93% of time when partner alights by mate (289). No particular order, but often begins with mutual Fencing display while giving either Crow or Laugh calls, giving way to mutual bowing and allopreening, though the opposite order can occur. Up to egg-laying within 2 min of landing, male mounts female regardless of whether sperm is transferred; thus, likely a part of pair-bonding. Among partners, 1.3 allopreens occur/bird/min; average duration 14.3 s. Pairs engage in Mutual Bowing display (see drawings and photographs in 289) or Foot-looking display (8), which resembles larid nest-site selection display. Both members bow heads to the ground; one or both may manipulate nearby pebbles or objects. Late-laying pairs display more than early-laying pairs, which may promote subcolony synchrony (315). Murres experimentally forced to move their breeding-sites engaged in more Mutual Bowing than control birds (289).

During assembly below cliffs prior to first land-coming, participates in two forms of communal display, Water-dances and Joy-flights (38). Small groups patter over the sea, but never take flight, chasing one another, sometimes underwater; others may circle over the sea, sometimes at high altitude. The function of these behaviors are unclear.

Male initiates copulation with Crow Call and attempts to mount; female initiates with Mounting Invitation, assuming a crouched position and often giving Adow Call. Females give Adow during all successful copulations, while males usually switch to Barking or Laugh Call once mounted (291, 314; see Sounds: Vocalizations).

Pair bond duration is variable. Pairs remain together 3–4 yr at Isle of May, Scotland (316, range 1–8 yr in 8-yr study; also at Great Island, Newfoundland, AES). Two multi-year studies found a yearly divorce rate of 8.2% (Great Island, Newfoundland; 311) and 10.2% (Isle of May, Scotland; 317). Divorcing murre pairs have an initiating pair member, the one that initiates breeding with a new individual; the non-initiator is the other bird in the divorcing pair. Breeding success of the non-initiators either decreased (317) or remained low (311), as these birds often remain unpaired after divorce. Breeding success increased for new pairs (311) or only for the intruder/new mate (317). Differences in divorce rates may relate to mortality rate since divorces facilitated by availability of birds whose mates have disappeared (311).

Extra-Pair Copulations/and Paternity

Males vigorously defend mate and ward off attempted “rapes,” or forced extra-pair copulations (318). No threat postures precede such defense, unlike territorial squabbles. Female fertile period, when forced extra-pair copulation most valuable to a male, begins about 25 d before laying. Males spend more time at territory then, thus likely incurring some energetic cost. Copulation rates start to increase 25 d, and peak about 12 d, before laying (319).

Extra-pair copulations are common; males attempt to mount almost all females landing in the colony during the end of pre-laying period into early egg laying (289, 318). Extra-pair copulations account for 10% and 11.2% of copulations during fertile period, but only 6% and 7% successful, respectively (i.e., full cloacal contact; Skomer Island, Wales: 319; Great Island, Newfoundland: 314). Females rarely solicit or accept mountings other than from mates; males exploit any opportunity. A given male may attempt 0–32 forced extra-pair copulations/season (Gannet Islands, Labrador: 318) with EPCs increasing in frequency closer to the onset of egg laying. Sperm storage and, subsequently, sperm competition favor both mate-guarding and extra-pair copulations, a “mixed reproductive strategy”; greater reproductive success for males that succeed in extra-pair copulations. Colonies with higher EPC rates also appear to have higher pair copulation rates. Probability of forced extra-pair copulation about 10 times more frequent in females with versus without neighbors (318, 319). In contrast to these studies, Walsh et al. (314) found little evidence that forced EPCs were ever successful in cloacal contact/sperm transfer. In most cases of mounting by non-mate males, the female stood upright and the male fell off. Successful EPCs were associated with females switching mates or male mates returning late to the colony. Successful EPCs appeared to be initiated by females and usually involved reproductively successful neighbors (divorcing murres usually re-pair with successful neighbors, 311). Successful EPCs and pair copulation were significantly longer than unsuccessful ones (314); forced EPCs involving multiple males at the same time were not successful (no cloacal contact observed, duration too short; 314).

Two studies of extra-pair paternity have reported low rates: 7.8% (6/77 families, Skomer Island, Wales; 313) and 3.1% (2/64 families, Great Island, Newfoundland; 314), with similarly low levels reported for Thick-billed Murres (7%; 320).

Social and Interspecific Behavior

Degree of Sociality

Among the most social of colonial birds, breeding without a constructed nest, in direct bodily contact within large assemblages, and feeding in flocks (see below). Usually must nest close to one another to breed successfully; otherwise large gulls (Larus spp.) take eggs, chicks, and/or steal food brought to chicks (321; see Predation and kleptoparasitism, below). Where murres breed within boulders or other topography, densities can be much lower.

Benefits of coloniality may include ease at finding food (“information-center” hypothesis; 322; but see below); and most likely includes proximity to large persistent fish aggregations (179; see Diet and Foraging) or mates; maximizing available breeding habitat; and predator swamping—an important factor, given that chicks leave cliffs and flats only one-quarter grown (breeding synchrony also critical). Negative aspects of coloniality include depletion of food (by interference or exploitative competition) near to colony, competition for space, attraction of predators, increased chance of extra-pair matings, and increased transmission of disease and parasites (218, 323). High concentrations of foraging murres can exclude other seabirds from local areas (115).


When food in extremely short supply, as seen during El Niño at the Farallon Islands, California, adults may steal fish from one another, especially large fish offered to a small or satiated chick (27); seen also at the Isle of May, Scotland (324). Especially in periods of food shortage, murres can also be victims of kleptoparasitism by gulls, which swoop down to steal an exposed fish (321).


No recorded observations of playful behavior.

Nonpredatory Interspecific Interactions

Shares surface breeding habitat with Northern Fulmar (Fulmarus glacialis); Great Cormorant (Phalacrocorax carbo), Double-crested Cormorant (P. auritus), Brandt's Cormorant (P. penicillatus), Pelagic Cormorant (P. pelagicus), and Red-faced Cormorant (P. urile); Glaucous Gull (Larus hyperboreus), Great Black-backed Gull (L. marinus), Herring Gull (L. argentatus), Glaucous-winged Gull (L. glaucescens), and Western Gull (L. occidentalis); Red-legged Kittiwake (Rissa brevirostris) and Black-legged Kittiwake (R. tridactyla); Thick-billed Murre; and at times Razorbill. Other species can use crevices or burrows within these habitats (e.g., Razorbill, Cassin's Auklet [Ptychoramphus aleuticus], Tufted Puffin [Fratercula cirrhata], and storm-petrels [e.g., Oceanodroma spp.; 325). On the one hand, interspecific displays have been observed between Thick-billed Murres and Common Murres, e.g., allopreening (P. Rodewald, personal communication), but on the other Common Murres displace Thick-billed Murres where competition for breeding ledges occurs; at Gannet Islands, Labrador, Thick-billed Murre take narrower ledges, leading to lower breeding success (326, 327, 192). Also displaces kittiwakes (38). At Farallon Islands, California, displaced by sea lions (Zalophus californianus) from gently sloping or flat terrain, but during period of population expansion, in turn, displaces Brandt's Cormorant and Western Gull; could not displace Pelagic Cormorant, as latter nest on thin ledges (99, DGA; see Breeding: Nest Site). In fact, at low breeding site numbers, by occupying spaces between, e.g., cormorant nests, protection is gained from aerial predators (DGA; see for instance JNCC [328] colony catalog showing many multispecies seabird colonies with low numbers of murres). Colony on Walrus Island, Pribilof Islands, Alaska (a low-lying, flat island), extirpated by expansion of northern sea lion (Eumetopias jubatus) rookery, from 1 million murres in 1953 to none by 1976 (329; see Demography and Populations: Population Status).

Participates in multispecies foraging flocks (to thousands of birds) that include shearwaters (Puffinus, Ardenna spp.), cormorants, gulls, jaegers (Stercorarius spp.), kittiwakes, other alcids, and marine mammals (whales : fin [Balaenoptera physalus], minke [B. acutorostrata], and humpback [Megaptera novaeangliae]; dolphins and porpoise: pilot whale [Globicephala melaena], white-beaked dolphin [Lagenorhynchus albirostris], harbor porpoise [Phocoena phocoena]); sometimes follows kittiwakes and other gulls to fish schools, where by diving, in turn, forces prey within reach of surface foragers (330, 331, 332, 333, DGA). As assessed during summer in semi-protected waters of Barkley Sound, British Columbia, however, most foraged away from multispecies flocks (H. R. Carter and S. G. Sealy, unpublished data); in offshore waters of central California, present in 15% of observed flocks (111). In Bering Sea, surface-feeding species take prey injured by diving murres (221); in Barkley Sound, California Gull (L. californicus) and Glaucous-winged Gull cue strongly on murres that concentrate schooling prey (e.g., herring Clupea spp.; 334, 128; see also Diet and Foraging).

Foraging disrupted by large numbers of diving shearwaters and Northern Gannet (Morus bassanus; 331, 333). However, concentrated foraging murres can exclude shearwaters from local areas (115). Association with feeding cetaceans mainly passive, as both feed on same prey, unlike surface-foraging species that depend on cetaceans to drive prey to the surface (333, DGA). Association with foraging large fish, e.g., salmon (Onchorhynchus spp.), perhaps also mainly passive (115).


Kinds of Predators

Natural predators of adults: birds of prey—Bald Eagle (Haliaeetus leucocephalus), Gyrfalcon (Falco rusticolus), Peregrine Falcon (F. peregrinus), Rough-legged Hawk (Buteo lagopus), Northern Goshawk (Accipiter gentilis), Snowy Owl (Bubo scandiaca); mammals—red fox (Vulpes vulpes) , arctic fox (Alopex lagopus), and polar bear (Ursus maritimus). Natural predators of eggs and chicks: birds—large gulls, Common Raven (Corvus corax), crows (Corvus spp.); mammals—red fox, arctic fox, least weasel (Mustela nivalis), and short-tailed weasel (M. erminea; 335, 38, 16, 336, 337, 34, 338, 192, 321, 339, 340, 341, 159, 342). During years of poor food availability in California Current, Brown Pelican (Pelecanus occidentalis) prey on murre chicks, which can cause colony abandonment (343). Infrequent predators include gray seal (Halichoerus grypus) and California sea lion, which are reported to take chicks on occasion (344, 345); large fish, such as Atlantic cod (Gadus morhua), taken with adult murres in stomachs (38). Introduced carnivorous mammals take adults, but mainly eggs and chicks—red fox, arctic fox, domestic dogs (Canis familiarus), rats (Rattus rattus, R. norvegicus), ground squirrels (Citellus spp.), and house mouse (Mus musculus; 335, 346, 347, 348, 323; see Conservation and Management: Effects of Human Activity).

Manner of Depredation

Falcons and eagles take adults on wing, usually near colonies as adults arrive or leave; other predators take adults on breeding ledges (339, 340, 159). Only (larger) female Peregrine Falcons take adults; must be within about 2 km of shore or falcon risks landing with prey in the sea (DGA). Eggs and chicks taken on breeding ledges by corvids, gulls, pelicans, and foxes, especially when adults leave in response to seeing a fox, falcon, eagle, or human nearby; cliff-top breeders particularly vulnerable, although breeding by large numbers in cliff-top habitats may be a temporary artifact of rapid population change (192, 340, 341, 159). Ravens pull single adults from eggs and from cliff (349). Large gulls take chicks walking (versus flying/falling) from ledges, if space between parent and chick too large (DGA). Pinnipeds seen taking chicks just after latter reach the sea (344, 345). Peregrine Falcons apparently take Thick-billed Murre chicks jumping from high ledges (5); the same would be likely for Common Murre. On rare occasions away from colony, young chicks taken by gulls and pinnipeds, if separated from adult; adults sometimes also taken (350, 344, 345). Very occasionally Great Black-backed Gull (Larus marinus) kill adult, incubating murres at Skomer Island (T. R. Birkhead, personal observation).

Response to Predators

Temporarily evacuates colony when large avian and mammalian predators appear; persistent predator presence leads to colony desertion (347, 192, 339, 340, 342). Numbers and size of colonies in Oregon changed as Bald Eagle population recovered, studied 1988–2013; number decreased by 50% where eagles most dense, but increased elsewhere where few eagles (342; see Conservation and Management). Recovery of eagle populations is now recognized as an important factor in breeding failures and population declines for colonies in the Pacific Northwest of North America, the northwest Atlantic, and northern Europe; both caused by direct predation and indirectly, by causing murres to flush, allowing gulls to take eggs and chicks (351). If threat not perceived as severe, murres circle and re-land; if severe, birds join rafts on water below cliffs; highest tendency to leave during prelaying (340). Colonies sensitized to aerial predators evacuate in response to any large bird (e.g., gull, heron [Ardeidae]; 340, DGA).

Most effective measure against gulls and corvids is for breeders to sit tightly on eggs and chicks; as a group, persistent lunging usually discourages predator (308).

Ultimately, habits of breeding on cliffs and remote islands (352, 218, 192, 323), breeding colonially (353), chicks leaving the colony at dusk (DGA), and highly synchronized breeding are evolutionary responses heavily influenced by predation (308, 354, 323; see Breeding: Fledging Stage). Predation or presence of predators can negatively affect both breeding success and timing of breeding (218, 339, 340: see Demography and Populations: Measures of Breeding Activity). Presence of falcons can also increase reproductive performance, and ultimately colony size, by deterring egg predators (gulls, crows, e.g., Tatoosh Island, Washington; 338).

At sea, escapes aerial or surface predators (or disturbances, e.g., boats) by diving or skittering across water surface half-flying/half-diving (i.e., wings held as when diving subsurface). Behavior (especially diving) often preceded by “intention movement” of dipping head repeatedly underwater, as if unsure whether to fly or dive (35).

Recommended Citation

Ainley, D. G., D. N. Nettleship, and A. E. Storey (2021). Common Murre (Uria aalge), version 2.0. In Birds of the World (S. M. Billerman, P. G. Rodewald, and B. K. Keeney, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.commur.02