Common Guillemot
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| Common Guillemot / Common Murre | ||||||||||||||||||||||||||
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| Uria aalge (Pontoppidan, 1763) |
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Colymbus aalge Pontoppidan, 1763 |
The Thin-billed or Common Murre (Uria aalge), also called Common Guillemot, is a relatively large auk. It spends most of its lifetime at sea, only coming to land to breed on rocky cliff shores or islands.
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[edit] Description
Adult birds are 38-46 cm in length with a 61-73 cm wingspan and weigh 945-1044 g when fully grown. They are black on the head, back and wings, and have white underparts. They have a thin dark pointed bill and a small rounded dark tail. The face becomes white in winter with a dark spur behind the eye. The chicks are downy in appearance with blackish on top and white below.
The bird is a fast, agile flier. The wings flap quickly and continuously in a straight line along the sea surface.
Western European birds of the subspecies U. a. albionis are dark brown rather than black, most obviously so in colonies in southern Britain. Some individuals in the North Atlantic, known as Bridled Guillemots, have a white ring around the eye extending back as a white line. They are not a distinct subspecies however, but a polymorphism which becomes more common the farther north the birds breed - perhaps character displacement with the northernly Brünnich's Guillemot, which has a white bill-stripe but no bridled morph. The white is highly contrasting especially in the latter species and would provide an easy means for an individual bird to recognize conspecifics in densely-packed breeding colonies.[1]
Common Murres have a variety of calls, including a soft purring noise.
[edit] Distribution and status[1]
The breeding habitat is islands, rocky shores, cliffs and sea stacks on:
- North Atlantic coasts, in North America as far south as New Brunswick, and in Europe as far south as Portugal.
- The north Pacific coasts of Alaska and British Columbia down to California. On the Asian side it breeds in Russia and Hokkaidō.
Some birds are permanent residents; northern birds migrate south to open waters near New England, southern California, Japan, Korea and the western Mediterranean.
The breeding population is large, at over two million pairs. It is presently stable, but potential threats include excessive hunting (legal in Newfoundland), pollution and oil spills.
[edit] Ecology and behaviour
Common Murres can venture far from their breeding grounds to forage; distances of 100 km and more are often observed[2] though if sufficient food is available closer by, the birds will venture much shorter distances. These birds are surface-divers which forage for food by swimming underwater using their wings for propulsion. Dives usually last less than one minute, but the birds hunt underwater for distances of over 50 meters on a regular base. Diving depths up to 50 m have been recorded and birds can remain underwater a couple of minutes, for a maximum recorded underwater distance of 180 m. U. aalge mainly eat small schooling fish 200 mm long or less, such as polar cod, capelin, sand lances, sprats, sandeels, Atlantic cod and Atlantic herring. Capelin and sand lances are favorite food, but what the main prey is at any one time depends much on what is available in quantity[2]. They also eat some molluscs, marine worms, squid, and crustaceans such as amphipods. They consume 20-32 grams of food in a day on average. They are often seen carrying the fish in their bill with the fishtail hanging out.[1]
[edit] Reproduction
Courtship displays including bowing, billing and preening. The male points its head vertically and makes croaking and growling noises to attract the females. As usual for auks, the species is monogamous. The colonies are densely-packed, with up to twenty pairs occupying one meter square at peak season. The islands can also be inhabited by other species, which mingle with the murres to varying extent.
They usually nest in tight-packed colonies (known as "loomeries") and lay their eggs on bare rock ledges or ground. The eggs are pointed, so that if disturbed they roll in a circle rather than fall off the ledge. Eggs are laid between May and July for the Atlantic populations and March to July for those in the Pacific. The eggs vary in colour and pattern to help the parents recognize them, each egg is unique. Colours include white, green, blue or brown with spots or speckles in black or lilac. Both parents incubate the egg for 28 to 34 days, swapping in twelve hour shifts.
The chicks will leave the nest after 18 to 25 days, by simply jumping down into the sea, slowing their fall by fluttering as they are not yet able to fly. Once the young chicks have left the nest the male teaches them how to dive and catch fish for up to two months. The chicks learn to fly roughly two weeks after fledging. Up until then the male feeds and cares for the chick at sea. In migration the chick swims about 1000 km. Common Murres only breed when they reach four to six years old. The lifespan is about 20 years.
[edit] Footnotes
[edit] References
- Bennett, J. (2001): Animal Diversity Web - Uria aalge. Retrieved 2008-JAN-13.
- BirdLife International (2004). Uria aalge. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes justification for why this species is of least concern
- Harrison, Peter (1988): Seabirds (2nd ed.). Christopher Helm, London. ISBN 0-7470-1410-8
- Lilliendahl, K.; Solmundsson, J.; Gudmundsson, G.A. & Taylor, L. (2003): Can surveillance radar be used to monitor the foraging distribution of colonially breeding alcids? [English with Spanish abstract] Condor 105(1): 145–150. DOI: 10.1650/0010-5422(2003)105[145:CSRBUT]2.0.CO;2 HTML abstract
- National Geographic Society (2002): Field Guide to the Birds of North America. National Geographic, Washington DC. ISBN 0-792-26877-6
- Nettleship, David N. (1996): 2. Common Murre. In: del Hoyo, Josep; Elliott, Andrew & Sargatal, Jordi (eds.) (1996), Handbook of Birds of the World (Volume 3: Hoatzin to Auks): 709-710, plate 59. Lynx Edicions, Barcelona. ISBN 84-87334-20-2
- Sibley, David Allen (2000): The Sibley Guide to Birds. Alfred A. Knopf, New York. ISBN 0-679-45122-6
[edit] External links
- USGS Patuxent Wildlife Research Center: Common murre Uria aalge.
- Common Murre Restoration Project
- Project Puffin:- Common Murres
