Thick-billed murres are stout seabirds with black feathers covering their head, back, and wings. White feathers cover their breast and underside. During winter, their neck and face become a paler grey. Their spear-shaped bills are grey-black and they have a white line running along the sides of the upper bill. Thick-billed murres can be distinguished from common murres by their thicker features, which include a heavier head and neck and a short, stout bill. Their back also appears blacker than common murres and they do not have as much brown streaking on their flanks. Thick-billed murres are diving birds with webbed-feet and short legs and wings. Their feet are set far back on their body, giving them a distinct upright posture, closely resembling the stance of a penguin. Male and female thick-billed murres look similar. Juveniles resemble adults in terms of plumage, but have a smaller, more slender bill. ("Encyclopedia of Life", 2012; "National Park Service", 2012; Hallvard, 2012; "National Geographic", 2012)
Thick-billed murres, or Brunnich's guillemots (Uria lomvia), are found flying over, swimming in, or living near Arctic and sub-Arctic waters. During the summer breeding season, these migratory waterbirds can be found as far south as the rocky coasts of Alaska, Newfoundland, Labrador, Greenland, and Scandinavia, as well as the Kuril Islands in Russia. During the winter, thick-billed murres move to open water on the edge of open ice. They are found southward to Nova Scotia and northern British Columbia and off the coasts of Greenland, northern Europe, the Mid-Atlantic, the Pacific Northwest of the United States, and southward in the Pacific Ocean to central Japan. After large storms, they are sometimes found further south or inland from their normal winter range. ("Encyclopedia of Life", 2012; "ICUN Red List", 2012; Gaston, et al., 2011; "National Geographic", 2012)
Thick-billed murres are marine birds and remain along sea coasts as far offshore as the continental shelf edge. This species is mostly found in large flocks out to sea in the open ocean during winter, but some are blown inland and may appear in bays, estuaries, or reservoirs. They are able to dive deeper in the water than most other birds, reaching depths of more than 100 meters (330 feet) in pursuit of prey. However, they typically do not dive that far and are considered 'mid-water feeders'. Once they are in flight, thick-billed murres can reach speeds of 75 mph, although, due to their awkward takeoff, they swim far better than they fly. Thick-billed murres gather in large groups on rocky coasts where the female lays her egg on a narrow ledge along a steep sea cliff; rarely, they may gather instead in caves or crevices. Murres are found in greater numbers on islands rather than on mainland coasts. ("Encyclopedia of Life", 2012; "ICUN Red List", 2012; Gaston, et al., 2011; "National Geographic", 2012)
There is little information on the mating systems of thick-billed murres; however, they may be similar to their close relative, common murres. Common murres typically have only one mate at a time. Before the eggs are laid, females are sometimes present in the colony; however, males are continuously present in the colony. With many of the mates absent, the number of mating events outside of the pair increases. Generally, females resist these advances and males vigorously defend their mates from other males. (Birkhead, et al., 1985)
Thick-billed murres begin breeding when they are five to six years old and nest in large dense noisy colonies on narrow cliff ledges. Within their colony, birds stand side by side, forming a tight-knit nesting habitat to protect themselves and their chicks from predators. Thick-billed murres typically arrive at nesting sites in the spring, from April to May, but because ledges are often still covered in snow, egg laying does not begin until the end of May or early June, depending on sea temperatures. Females all lay their eggs at approximately the same time so all of the chicks hatch around the same time. Once they are juveniles, they will all jump off breeding ledges into the sea together and undertake their long migration to wintering grounds. Females lay a single egg with a thick-heavy shell, which is often a greenish to pinkish hue, with other patterns of color. Eggs are pear-shaped, so they do not roll when jostled. Females arrange pebbles and other debris close to their eggs instead of building nests. They also secure the egg in place with feces, to prevent the egg from rolling off the ledge. Both males and females take shifts incubating the egg with their weight directly on the egg, over the course of an average 33-day period. The egg hatches in 30 to 35 days, with both parents involved in the care of the chick until it fledges at about 21-days-old. ("ICUN Red List", 2012; "National Park Service", 2012; Hallvard, 2012; Herzberg, et al., 2003; Hipfner and Gaston, 1999; "Global Species", 2012; "National Geographic", 2012)
Thick-billed murres live their lives similar to other marine birds. They wait several years to begin breeding, and when they do, they lay one egg at a time. As females age, they lay larger eggs and begin laying their eggs sooner in the season. If they lose an egg during the breeding season, there is only about a 20 to 30% chance of a female re-laying an egg. Generally, the only females that lose their eggs are young and inexperienced. If they do lay a replacement egg, the egg is usually 5 to 6% smaller, compared to the first egg. Thick-billed murres have a largely precocial post-hatching development, meaning the chicks are larger and more independent than some other species. (Herzberg, et al., 2003)
In this species, both males and females give a great amount of care to their single-egg. Both incubate the egg constantly, taking shifts of 12 to 24 hours over a 33-day period, when it hatches. The nestling is then fed, mainly fish, by both parents at the breeding site for approximately 15 to 30 days. Usually, it fledges at about 21-days-old. After that point, the female departs for the sea. The male parent stays to care for the chick for a longer period of time, after which, he and the chick leave the breeding grounds and go to the sea, leaving at night during calm weather. Males spend 4 to 8 weeks with the chick before it is independent. ("National Park Service", 2012; Gaston, et al., 2005; Hallvard, 2012; "National Geographic", 2012)
In the wild, thick-billed murres can live up to 25 years on average. Female birds reach reproductive maturity at 5 to 6 years of age. In northeastern Canada, adult bird's yearly survival rate was estimated at 91%. Whereas, the survival rate of young birds from the time they are independent until they are three years of age was estimated to be 52%. Thick-billed murres are vulnerable to threats from human sources, such as oil spills and gill-netting. In some regions, they are hunted for food by communities in Alaska and Canada. ("Encyclopedia of Life", 2012; "National Park Service", 2012; "Global Species", 2012; "National Geographic", 2012)
Thick-billed murres gather in large dense colonies on cliff ledges where breeding occurs. These birds dive at depths greater than 100 meters into the ocean in pursuit of fish, squid and crustaceans. They are great flyers, although, due to their awkward takeoffs, they are better swimmers. Adult and juvenile thick-billed murres swim large distances in migratory journeys away from their breeding colonies, towards their rearing and wintering area. Upon fledgling, chicks can swim nearly 1,000 kilometers (620 miles) accompanied by their male parent in the first leg of the journey to their wintering grounds. During this time, adults molt into their winter plumage and temporarily lose their ability to fly until they re-grow their flight feathers. Thick-billed murres are generally active during the day. ("Encyclopedia of Life", 2012; Hallvard, 2012; "National Geographic", 2012)
Thick-billed murres travel 10 to 168 km one-way to foraging sites. Foraging patterns of a population of thick-billed murres breeding in northwestern Iceland were tracked using bird-borne data loggers. (Benvenuti, et al., 1998)
Thick-billed murres communicate vocally. Among chicks, calls are mainly flute-like and their departure call rapidly changes frequency. Such calls are given shortly before, during, and after they leave the colony as fledglings, as a mode of communication between the chick and the male parent caring for them. Adult calls, in contrast, are lower pitched and sound gruffer. Based on the closely related common murre, the calls are heavy, resembling a laughing “ha ha ha” sound, or a longer, growling sound. In aggressive behaviors, common murres emit a weak, rhythmic vocalization. There are variations in pitch, duration and syllables of calls given by adults. This variation may mean that the birds can recognize others just by their calls, especially among parents and chicks. (Hallvard, 2012; Lefevre, et al., 2011)
Although there is little information specific to thick-billed murres, there is a great deal of information about aquatic birds in general. For instance, the vision of aquatic birds is limited underwater; however, their eyes may be specialized to make up for this loss. (Sivak, 1980)
Thick-billed murres are carnivorous and have been known to consume a variety of marine species, including pollock, sculpin, flounder, capelin, sand eel, Atka mackerel, squid, Arctic cod, annelid worms, crustaceans, and large zooplankton. Uria lomvia forage underwater at depths greater than 100 meters, in waters less than 8 degrees Celsius. ("ICUN Red List", 2012; "National Park Service", 2012; Bradstreet, 1980; "Global Species", 2012)
The foraging behavior of U. lomvia varies based on the type of prey they are after and the habitat they are in. They usually return to the colony with only one prey item, except when they capture invertebrates. Thick-billed murres spend less energy capturing low quality prey and more energy on capturing high quality prey. Thick-billed murres invest more energy in diving for swimming mid-water prey items in active pursuit. On the other hand, murres spend a greater deal of time, but less energy, searching for prey located on the sea floor, gliding slowly along the bottom searching in the sediments or under rocks. Thick-billed murres may also have differences in their diet based on their habitat. While they are near offshore ice edges, they feed in the water and under the ice attached to land. In contrast, when they are on coastal ice edges, thick-billed murres feed under ice, on the sea bottom, and in the water. (Elliott, et al., 2009; Gaston, et al., 2005)
The main predators of thick-billed murres are in the sky, including common ravens, eagles, and gulls. Glaucous gulls are known to prey particularly upon murre eggs and unattended chicks. However, the dense nesting colony of thick-billed murres, in which the birds stand side-by-side in tight-packed aggregations, helps protect adults and their young from predators in the sky and those on land, particularly arctic foxes. ("National Park Service", 2012; Hallvard, 2012)
Thick-billed murres eat fish and many other marine organisms discussed above. They are also prey for common ravens, eagles, gulls, and arctic foxes. In addition, they can become infected with marine parasites, including species of parasitic nematodes, by eating infected fish. ("National Park Service", 2012; Hallvard, 2012; "Global Species", 2012)
Based on their pattern of foraging, these seabirds play a role in marine ecosystems. Thick-billed murres track the movement of prey, such as capelin. This indicates that capelins are a high quality prey items because the murres invest a lot of energy in their capture. The quantity of prey in a certain area can impact the hunt. Small schools of fish and crustaceans can quickly form larger groups to ward off predators. Thick-billed murres search for large groups of their prey, they are able to achieve this because they can travel long distance and turn quickly. Once they locate larger groups, they are able to shorten the distance they have to search. ("National Park Service", 2012; Fauchald, et al., 2000; "Global Species", 2012)
There are no known adverse affects of U. lomvia on humans.
Towards the Arctic region, thick-billed murres are often hunted as a food source. Canadian natives shoot the birds near their breeding colonies or during their migration from the coast of Greenland each year in a traditional food hunt. In addition, certain groups, such as Alaskan natives, collect murre eggs for food. In the 1990s, an average household on St. Lawrence Island (located west of mainland Alaska in the Bering Sea) consumed 60 to 104 murre eggs annually. ("National Park Service", 2012; "National Geographic", 2012)
Because they nest in such large colonies, thick-billed murres are an indicator species for researchers. Changes in the availability of food or environmental pollution, for example, can result in large numbers of dead murres washing ashore. ("National Park Service", 2012; "National Geographic", 2012)
As one of the most numerous seabirds in the northern hemisphere, the global population of thick-billed murres is healthy and is estimated to number greater than 22,000,000 individuals, over a large range. Therefore, this species does not approach the thresholds for a vulnerable species. However, threats remain, especially from oil spills and gill-netting, as well as an increasing numbers of natural predators, such as gulls. ("ICUN Red List", 2012; Hallvard, 2012)
This species is named after Morten Thrane Brünnich, a Danish zoologist. ("Global Species", 2012)
Roselyn Thalathara (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
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