The term Guillemots refers to a fascinating group of seabirds within the auk family, known for their striking black-and-white plumage, agile diving abilities, and cliff-nesting habits. These birds are highly adapted to the marine environment, spending much of their lives at sea and only coming ashore to breed. Guillemots are divided into two distinct genera, Uria and Cepphus, each with unique characteristics and evolutionary histories. Their remarkable behaviors and ecological roles make them a captivating subject for birdwatchers, nature enthusiasts, and wildlife photographers alike. This article explores the taxonomy, distribution, appearance, behavior, breeding, conservation, and intriguing facts about these remarkable birds.
Scientific Classification
Guillemots belong to the family Alcidae, commonly known as the auk family, which also includes puffins, murres, razorbills, and the extinct great auk. The group is primarily divided into two genera: Uria and Cepphus. The genus Uria includes the Common Guillemot or Common Murre (Uria aalge) and Brünnich’s Guillemot or Thick-billed Murre (Uria lomvia). These species are closely related to other members of the tribe Alcini, which encompasses birds such as the Razorbill (Alca torda) and the Dovekie (Alle alle), as well as the extinct Great Auk (Pinguinus impennis), which was once found in the North Atlantic but was driven to extinction in the 19th century.
The genus Cepphus contains three species: the Black Guillemot or Tystie (Cepphus grylle), the Pigeon Guillemot (Cepphus columba), and the Spectacled Guillemot (Cepphus carbo). Unlike Uria, the Cepphus species form their own tribe called Cepphini, distinguished by their slightly different morphology and ecological preferences.
Fossil records reveal that prehistoric species of both genera existed millions of years ago. For example, Uria bordkorbi from the Late Miocene found in California is notable for being the only known Alcini fossil outside the Atlantic region, suggesting that these birds’ evolutionary origins may extend to the Caribbean or near the Isthmus of Panama, contrary to previous beliefs that they evolved solely in the Atlantic. Similarly, fossils of Cepphus species from the Miocene and Pliocene epochs have been found along the western coast of the United States, providing insights into their historical distribution and evolution.
Geographic Range & Distribution
Guillemots are primarily distributed throughout the cooler waters of the Northern Hemisphere, with species ranges spanning the North Atlantic and North Pacific Oceans. The two genera occupy somewhat distinct geographic regions, although there is some overlap.
The Common Guillemot (Uria aalge) has a broad distribution across the North Atlantic, ranging from the eastern coasts of North America, including Newfoundland and Labrador, across to the coasts of Europe and western Asia. They are widespread around the British Isles, Scandinavia, Iceland, and as far north as the Arctic Ocean. In the North Pacific, the closely related Brünnich’s Guillemot (Uria lomvia) occupies Arctic and subarctic waters, breeding along the coasts of Alaska, Siberia, and northern Canada. This species is more adapted to colder, polar environments compared to the Common Guillemot.
The Cepphus genus species have a slightly different distribution. The Black Guillemot (Cepphus grylle) is found in the North Atlantic, from the eastern coast of North America to Greenland, Iceland, and northern Europe. The Pigeon Guillemot (Cepphus columba) inhabits the North Pacific coastline, from Alaska down to California, favoring rocky shorelines and islands. The Spectacled Guillemot (Cepphus carbo) is more restricted to the northern Pacific coasts of eastern Russia and northern Japan.
Guillemots typically breed on rocky cliffs and islands, choosing locations that provide protection from terrestrial predators and easy access to the sea for feeding. Outside the breeding season, they spend most of their time at sea, often traveling long distances in search of food.
Physical Description
Guillemots are medium-sized seabirds characterized by their streamlined bodies, which are highly adapted for diving and swimming underwater. Members of the genus Uria are generally larger than those in Cepphus, with adults measuring between 38 to 45 centimeters (15 to 18 inches) in length and sporting a wingspan of approximately 61 to 73 centimeters (24 to 29 inches). Their weight ranges from 600 to 1,000 grams (1.3 to 2.2 pounds), with Brünnich’s Guillemot tending to be slightly larger and heavier than the Common Guillemot.
These birds have predominantly black or dark brown upperparts and white underparts, providing effective counter-shading camouflage in the marine environment. Their slender, pointed bills are black and designed for catching slippery prey underwater. The Common Guillemot has a long, thin bill, while the Thick-billed Murre has a noticeably more robust and thicker bill, which helps distinguish the two species.
In contrast, the Cepphus genus species are smaller, generally measuring 30 to 38 centimeters (12 to 15 inches) in length with wingspans between 50 and 60 centimeters (20 to 24 inches). They exhibit more varied plumage, often including distinctive white wing patches and striking facial markings. For example, the Black Guillemot is mostly black with large white wing patches visible in flight, while the Spectacled Guillemot is known for its white facial ring that resembles spectacles, a feature that gives the bird its common name.
During the non-breeding season, the plumage of some species undergoes subtle changes, becoming duller or mottled to provide better camouflage at sea. Juveniles generally have more muted coloration and shorter bills until they mature.
Behavior & Diet
Guillemots are renowned for their exceptional diving and swimming abilities. They use their wings to “fly” underwater, propelling themselves with powerful wing beats to chase and capture prey. Their streamlined bodies and strong legs positioned far back on the body optimize them for aquatic life, though this makes them somewhat clumsy on land.
Their diet primarily consists of small fish and invertebrates. Common prey items include schooling fish such as sand lance, capelin, herring, and sprat, as well as crustaceans and marine worms. Guillemots typically dive to depths ranging from 20 to 100 meters (65 to 330 feet), with some dives lasting up to a minute or more. Brünnich’s Guillemot, for example, is known to dive deeper and for longer durations than its Common Guillemot counterpart, adapting to the Arctic environment where prey may be more dispersed. According to RSPB, this species is well documented.
These birds forage in groups, often following schools of fish near the surface. They are also known to feed during both day and night, taking advantage of seasonal fish migrations and plankton blooms. On land, guillemots are social birds, forming large, dense colonies on steep cliffs where they nest in close proximity to one another. According to eBird, this species is well documented.
Breeding & Reproduction
Guillemots breed in large, dense colonies on rocky cliffs and islands, locations that provide safety from land predators and access to rich feeding areas at sea. Their breeding season typically begins in spring, coinciding with the abundance of fish that will feed the chicks.
The Common Guillemot lays a single egg directly on bare rock ledges without building a nest. The egg is uniquely shaped—pyriform or pear-like—designed to roll in a tight circle rather than off the cliff ledge, an adaptation to their precarious nesting sites. The egg’s coloration and patterning provide camouflage against the rocky background.
Incubation lasts about 30 to 35 days, during which both parents share the responsibility of keeping the egg warm. Once hatched, the chick is semi-precocial, covered with down and able to regulate its temperature but dependent on parents for food. Guillemot chicks have a remarkable behavior known as the “jump,” where they leave the nest ledge before they can fly—often at just 20 to 25 days old—and leap into the sea below. The male parent typically accompanies the chick at sea, feeding it until it fledges, which can take several weeks.
Breeding success depends heavily on food availability and environmental conditions. Colony sites are often traditional and used year after year, with birds displaying strong site fidelity.
Conservation Status
The International Union for Conservation of Nature (IUCN) currently lists most guillemot species as of Least Concern, reflecting their widespread distribution and relatively stable populations in many areas. The Common Guillemot (Uria aalge) and Brünnich’s Guillemot (Uria lomvia) both hold this status, though local populations can be vulnerable to specific threats.
Major threats to guillemots include oil spills, overfishing of their prey species, climate change, and disturbance or destruction of breeding sites. Oil pollution is particularly hazardous because it affects the birds’ waterproofing and insulation, often leading to hypothermia. Additionally, changes in sea temperature and fish populations due to climate change can affect food availability, impacting breeding success.
Some populations, especially in the Arctic, may face increased pressures from habitat changes and human activities such as shipping and resource extraction. Conservation efforts focus on monitoring populations, protecting breeding colonies, regulating fisheries, and mitigating pollution risks.
Interesting Facts
Guillemots are remarkable for their ability to “fly” underwater using their wings, making them among the most efficient diving birds. Their wing muscles are powerful and adapted for rapid underwater strokes, allowing them to catch agile prey in a three-dimensional aquatic environment.
Their iconic nesting behavior, where chicks leap from cliff ledges into the sea before they can fly, is both extraordinary and perilous. This leap is a critical survival strategy, as remaining on the ledges longer increases exposure to predators and harsh weather. The male parent’s role in escorting and feeding the chick at sea highlights a fascinating aspect of their parental care.
Guillemots are also important indicators of marine ecosystem health. Changes in their population size, breeding success, or diet composition can reflect alterations in fish stocks and ocean conditions, making them valuable species for ecological monitoring.
Finally, the name “guillemot” is believed to derive from the French word “guillemot,” which itself may have origins related to the Germanic personal name Wilhelm, though the exact etymology remains uncertain.
Conclusion
Guillemots are captivating seabirds that combine striking appearance, specialized diving abilities, and unique breeding behaviors. Their presence across the northern oceans and their adaptations to life at sea showcase the incredible diversity and resilience of marine bird species. As sentinels of ocean health and key players in coastal ecosystems, guillemots deserve continued study and conservation attention. For birdwatchers and wildlife enthusiasts, observing these birds—whether witnessing their dramatic cliffside colonies or their agile underwater hunts—offers a glimpse into the dynamic world of seabird life.
