Overview
The Common Murre (Uria aalge), known across Britain and Europe as the Common Guillemot, is a sleek, black-and-white pelagic seabird belonging to the auk family Alcidae. Dominating the wild, spray-drenched sea cliffs and offshore stacks of the northern oceans, this resilient marine bird spends the vast majority of its life at sea, congregating on land only during the summer breeding season to form some of the densest and most deafening avian colonies on Earth.
Sporting an immaculate dark chocolate-brown head and back contrasting with a snow-white underbelly, Uria aalge looks remarkably like a northern hemisphere penguin, though unlike true penguins, it retains strong aerial flight. Flying underwater using its stiff wings as flippers to dive to staggering depths exceeding 180 meters (600 feet), the common murre is an elite marine pursuit hunter and a cornerstone bioindicator of oceanic ecosystem health.
AT A GLANCE
- Common Name: Common Murre
- Scientific Name: Uria aalge
- Category: Birds
- Subcategory: Auks
- Size: 38 to 46 cm (15 to 18 in) length; 61 to 73 cm (24 to 29 in) wingspan
- Weight: 850 to 1,150 g (1.9 to 2.5 lb)
- Lifespan: 20 to 25 years in the wild; maximum recorded over 32 years
- Diet: Piscivorous/Deep-diving Pursuit Hunter: small schooling pelagic fish (sand lance, capelin, sprats, herrings, cod), squid, and krill
- Habitat: Precipitous ocean sea cliffs, rocky offshore stacks, and open subarctic pelagic ocean waters and continental shelf upwellings.
- Range: Circumpolar boreal and low-Arctic distribution across the North Atlantic and North Pacific oceans, breeding from Alaska to California and Greenland to the British Isles and Norway.
- Conservation Status: Least Concern (IUCN Red List)
Biology and Physical Characteristics
Uria aalge exhibits extreme morphological specialization for underwater pursuit diving. Its heavy, dense skeleton reduces natural buoyancy, and its wings are short, narrow, and stiff, acting as powerful hydrofoils that beat through dense seawater with minimal flex. In breeding dress, its plumage is rich sooty-brown on the head, neck, and upperparts, with clean white underparts and a sharp, dagger-like black bill. In the North Atlantic, a distinct genetic morph known as the ‘bridled guillemot’ displays a white ring around the eye and a white line extending down the temple.
Its breeding anatomy is famous for its pear-shaped (pyriform) egg: laid directly on narrow, bare cliff ledges without a nest, the egg’s exaggerated conical shape ensures that if bumped by a seabird or wind gust, it pivots in a tight circle on its point rather than rolling off the edge of the cliff into the sea.
Behavior and Ecology
Common murres are oceanic wanderers that ride turbulent winter waves hundreds of miles offshore, feeding in rich coastal upwelling zones. When hunting, they plunge into the ocean, diving with ease to depths of 100 to 180 meters (330 to 600 feet) for up to two minutes to chase schooling sandeels and capelin.
In spring, millions gather on vertical sea cliffs, nesting shoulder-to-shoulder at staggering densities of up to 20 pairs per square meter. The pair incubates their single pyriform egg for 33 days. At just three weeks of age, before its flight feathers have grown, the tiny chick participates in a death-defying leap: encouraged by its father calling from the waves below, the flightless chick jumps off the cliff edge, tumbling hundreds of feet down into the surf, where the father guides it out to sea and teaches it to dive.
Conservation and Human Impact
The Common Murre is classified as Least Concern on the IUCN Red List, with a colossal global population estimated at 18 million individuals across the North Atlantic and Pacific. However, their high-density colonial lifestyle and surface-foraging habits make them exceptionally vulnerable to anthropogenic marine disasters.
Murres are chronically the most heavily affected seabirds in major marine oil spills, as floating oil coats their insulating plumage, causing rapid hypothermia and death. Massive gillnet bycatch, commercial overfishing of forage fish like capelin and sand lance, and catastrophic marine heatwaves driven by climate change (which caused millions of murres to starve in the Pacific in 2015-2016) represent critical ongoing challenges.
Interesting Factoid
Common murre eggs are shaped like spinning tops; if bumped on a narrow, foot-wide cliff ledge, the egg spins around its pointed tip in a tight circle instead of rolling off the cliff into the ocean.