Thick-billed Murre (Uria lomvia)

In its striking, immaculate black and white summer plumage, the thick-billed murre looks like it is wearing a dinner jacket. However, the fishy odours and loud, squawking commotion of a murre breeding colony do not suggest a polite dinner party!

Description

The thick-billed murre is an elegant seabird measuring 40-45 cm in length, the size of a small duck. Its upper parts, feet, head and neck are jet black, while its breast and belly are white. Thick-billed murres can be distinguished from common murres by their black, not brown plumage, and their thicker bills, which have a thin white line at the base. They also lack the white stripe behind the eye that is present in common murres. In winter, thick-billed murres are less glossy-looking, but still retain their black.

Distribution

Thick-billed murres and common murres are among Canada’s most common seabirds. While common murres remain in the southern, ice-free zones of the Atlantic and Pacific coasts, thick-billed murres are truly circumpolar, inhabiting the northernmost reaches of the Arctic coasts and islands. In Canada, colonies of thick-billed murres are located from the Bird Rocks in the Gulf of St. Lawrence, north along the coasts of Newfoundland and Labrador to Baffin and Ellesmere Islands.

Ecology

Like most members of the alcid family, thick-billed murres have short, stubby wings, and feet that are located far back on its body. This adaptation allows them to swim rapidly in pursuit of fish, squid and shrimp. This bird can dive to depths of 180 metres! Like penguins, murres use their wings to “fly” quickly through the water. Flying through the air, however, is a challenge- its narrow wings provide little lift for take-off and its tail is too small to give effective stability and steerage. Although it can fly rapidly once airborne- up to 75 km per hour- it must its large webbed feet behind it as a rudder to help steer, and often must make several attempts to land on the narrow cliff ledges where it nests.

Thick-billed murres nest by the thousands, in impressive colonies on cliff faces that are inaccessible to terrestrial predators. Unlike other alcids, they have very reduced territories- each bird only defends the area it can reach with its bill from where it sits on its egg. Nest density may reach as high as 10-30 eggs per square metre! Fortunately, murre eggs vary greatly in colour and mottling, from green to pinkish- otherwise parents might be unable to recognize their own egg. During the 4-week incubation period, males and females take two-day turns sitting on the egg while the other parent feeds out at sea. Murre eggs are round at one end and pointy at the other, a unique shape that ensures that if they are bumped accidentally, they will roll around in a circle instead of falling off the cliff. Cliff life does present many hazards, however, as storms, cold weather and disturbance by humans can cause both chicks and eggs to be blown or knocked off their narrow ledges, killed by exposure, or left undefended to be snatched by predatory gulls. Many more murres are hunted for their meat, drowned in fishing nets, or die as a result of oil spills. Hunting and egg-collection in the 19th and early 20th centuries caused a drastic drop in murre populations, which are only now showing signs of recovery. Thick-billed murres may live for at least 25 years, but do not reach maturity until 5 years of age.

After only three weeks of life, a thick-billed murre chick must plunge into adulthood- right off its high cliff ledge and into the cold ocean. Although they have fully waterproof feathers, chicks cannot fly when they leave the “nest”, and simply splash down onto the water, where they are joined by their parents. This dive usually occurs in the evening, to avoid the predatory gulls that swoop around the colony by day. On their first day after leaving the nest, chicks begin an incredible migration southward. First they swim up to 1000 km and then, once their flight feathers have developed, fly yet further south to their wintering grounds in polynyas or beyond the limit of winter sea ice. Adults also moult during the first part of this unique and remarkable journey and, during this time, are completely flightless. Murres nesting in the Maritimes usually winter along the coasts of the northern United States, but occasionally range as far south as Florida.