Thick-billed Murres or Bruünnich’s Guillemots (Uria lomvia) are a bird in the auk family (Alcidae). also known as the tuxedo seabird, is easily identifiable by its striking black and white plumage. This bird, which is often mistaken for a penguin because of its upright posture and colouration, is a highly skilled diver and flier, well adapted to life in cold northern oceans. It’s only found in the Northern Hemisphere and nests in large colonies on steep sea cliffs along the Arctic coast.
The Thick-billed Murre, named in honour of Danish zoologist Morten Thrane Brunnich, is also called Pallas’ Murre when it appears in the North Pacific, Uria Lomvia Ara. They can live up to a century and mate for life. Both parents travel long distances to deliver one fish to the chick. They spend most of the year in the open ocean, diving to incredible depths, and resting on floating glaciers between foraging trips.
Behaviour
The Thick-billed murres are social seabirds that gather in large colonies on steep Arctic seacliffs during the breeding season. The cliff edges become noisy and crowded as murres build nests next to each other, creating one of the densest seabird colonies in the world. These birds are capable of flying, but their real strength is in swimming. They are excellent underwater hunters, using their short wings for diving. They hunt fish, squid and crustaceans in depths often exceeding 100 meters.
Murres migrate to the sea after the breeding season. Both adults and young birds embark on long journeys. The chicks are unable to fly and leave the nest. They jump from the cliffs, swim up to 1,000 km with their male parent to reach the wintering grounds. Adults go through a complete moult during this migration. They lose their flight feathers and are temporarily unable to fly. It makes them vulnerable, but it also marks the beginning of their winter lifestyle, where they dive and hunt in the cold waters of northern Canada. Murres are active in daylight, which makes their dives and parental care more obvious to bird watchers
Habitat
The Thick-billed murre is a true sea creature, living most of its life along the Arctic coasts and in the open ocean. The thick-billed murres are seldom found in the interior, unless storms cause them to stray. In the non-breeding seasons, murres can be found in large flocks, far offshore. They are often seen near the edge of the continental shelf, where the nutrient-rich waters attract schools and schools of fish. Murres, despite their ungainly appearance on land, are extremely agile underwater. They are also among the deepest-diving seabirds. Some have even been observed diving more than 100 meters in search of food.
These murres breed on rocky seacliffs. They often nest on isolated islands, where they are safer from predators. The females simply lay one egg on the bare rocks of narrow cliff edges. No nest is needed. They nest occasionally in caves and crevices, but cliff faces are the best place to do so. They are more prevalent on islands than on the coasts of mainland Canada, and their dramatic nesting locations make them an important part of any Arctic wildlife tour. Thick-billed Murres, with their strong swimming ability and special habitat requirements, are an amazing example of seabirds surviving in one of Earth’s harshest environments.
Distribution / Range
It breeds on coasts and islands in the High Arctic of Europe, Asia and North America, where it is one of the most numerous bird species.
Description
At 40€“44 cm in length, with a 64€“75 cm wingspan, very similar in size to the closely related Common Guillemot (or Common Murre, U. aalge). The Pacific race (U. l. arra) is larger than the Atlantic race, especially in bill dimensions. Since the extinction of the Great Auk in the mid-19th century, the murres are the largest living members of the Alcidae.
Adult birds are black on the head, neck, back and wings with white underparts. The bill is long and pointed. They have a small, rounded black tail. The lower face becomes white in winter. This species produces a variety of harsh cackling calls at the breeding colonies, but is silent at sea.
They differ from the Common Murre in their thicker, shorter bill with white gape stripe and their darker head and back; the “bridled” morph (genetic mutation) 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. According to RSPB, this species is well documented.
In winter, there is less white on the Thick-billed Murre’s face. They look shorter than the Common Murre in flight. First-year birds have smaller bills than adults, and the white line on the bill is often obscure, making the bill an unreliable way to identify them at this age. The head pattern is the best way to distinguish first-year birds from Common Murres. According to eBird, this species is well documented.
Ecology
The Thick-billed Murres breed in large colonies on coastal cliffs, their single egg being laid directly on a cliff ledge. A description of the species’ breeding biology is given in detail by Gaston and Nettleship (1981).
Migratory Patterns
They move south in Winter into the northernmost areas of the North Atlantic and Pacific, but only to keep in ice-free waters. They are rare in temperate waters.
As a vagrant, Brünnich’s Guillemot is a rare vagrant in European countries south of the breeding range. In Britain, over 30 individuals have been recorded, but over half of these were tideline corpses. Of those that were seen alive, only three have remained long enough to be seen by large numbers of observers. All three were in Shetland – winter individuals in February 1987 and November/December 2005, and a bird in an auk colony in summer 1989. The 1989 and 2005 birds were both found by the same observer, Martin Heubeck.
The species has been recorded once in Ireland and has also been recorded in the Netherlands. In the western Atlantic, they may range as far as South Carolina, and in the Pacific to California. Before 1950, large numbers appeared on the North American Great Lakes in early winter, passing up the St. Lawrence River from the East Coast. Such irruptions have not been seen since 1952.
Flight and Feeding Characteristics
The Thick-billed Murres’ flight is strong and direct, and they have fast wing beats due to the short wings. These birds forage for food like other auks by using their wings to ‘swim’ underwater. They are accomplished divers, reaching depths of up to 150 m and diving for up to four minutes at a time; usually, however, birds make either shallow short dives or dive down to 21€“40 m for longer periods.
Adults mainly eat invertebrates and a few fish and provision their chicks with fish, squid, some crustaceans and other small invertebrates. They carry these prey items to their chicks, one at a time, in their bill. Birds will make long trips to get to their favourite feeding grounds; while they usually forage several dozen km from their nest sites, they often travel more than 100 km to fish.
The diving depths and durations regularly achieved by these birds indicate that they, and similar auks, have some as yet unknown mechanism to avoid diving sickness and lung collapse when surfacing. It is postulated that Auks temporarily absorb excess gases into the vascular structure of their bones. From there, it is gradually released from temporary storage in a controlled process of decompression.
Conservation Status
Egg harvesting and hunting of adult birds are major threats in Greenland, where populations fell steeply between the 1960s and 1980s. In the Barents Sea region, the species has declined locally due to influences associated with polar stations in Russia. Fisheries may also be a threat, but because Thick-billed Murres are better able to utilise alternative food sources, the effect of over-fishing is not as severe as on the Common Murre. Pollution from oil at sea exerts another major threat. Murres are among the seabirds most sensitive to oil contamination. Incidental mortality brought on by entanglement with fishing gear is also an important cause of population decline.
Thick-billed murres are closely associated with sea ice throughout the year. Consequently, some scientists believe that climate change may be a threat to this Arctic-breeding species. However, the species seems adaptable. Populations at the Southern edge of their range switched from feeding on ice-associated Arctic cod to warmer-water capelin as ice break-up became earlier. Dates for egg-laying advanced with the earlier disappearance of ice. The growth of chicks is slower in years when ice break-up is early relative to egg-laying by the murres. In extremely warm years, mosquitoes and heat kill some breeders.
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