Guillemot
Seabirds known for pear-shaped eggs and cliffside colonies.
Guillemot is the common name for several species of seabird in the Alcidae or auk family, part of the order Charadriiformes. In Europe, the term covers two genera, *Uria* and *Cepphus*, while in North America only the *Cepphus* species are called guillemots, with the *Uria* species known instead as murres. The word "guillemot" itself is of French origin, first recorded in 1555 by Pierre Belon, and is derived from older forms of the name William, ultimately onomatopoeic from the loud, high-pitched begging calls of young common guillemots. The American name "murre" is also onomatopoeic, mimicking the growling call of adult common guillemots.
The two living species of *Uria*—the common murre and the thick-billed murre—belong to the tribe Alcini, alongside the razorbill, little auk, and the extinct great auk. These birds have distinctly white bellies, thicker and longer bills than *Cepphus*, and form very dense colonies on cliffs during the breeding season. The three living species of *Cepphus*—the black guillemot, pigeon guillemot, and spectacled guillemot—form their own tribe, Cepphini. They are smaller, with black bellies in breeding plumage, rounder heads, and bright red feet.
Guillemots lay a single pyriform (pear-shaped) egg directly on a cliff edge, building no nest. This shape allows them to nest densely on uneven ledges, protecting eggs and chicks from predatory gulls. While the egg might seem prone to rolling off, experiments show that its long straight edge resting on the ground creates friction, making it less likely to move and fall. Guillemot eggs are large, around 11% of the female’s weight, and colourful, making them attractive to egg collectors. In Scotland’s St Kilda islands, eggs were collected until the late 1920s by men scaling cliffs, then buried in peat ash to be eaten through winter, and were considered similar in taste and nutrition to duck eggs. Guillemot chicks leave the nest by jumping from cliffs before their wings are strong enough for flight, parachuting down and bouncing slightly upon landing due to their dense downy feathers and underdeveloped wings.
- field
- Seabird biology
- known_for
- Pyriform eggs and cliffside breeding colonies
- species_count
- Five living species (two Uria, three Cepphus)
- egg_weight
- Around 11% of female weight
- egg_shape
- Pyriform (pear-shaped)
Lore & Background
Guillemots lay a single pyriform egg directly on a cliff edge in dense breeding colonies; they do not build a nest, allowing them to nest close to one another even on uneven cliff edges. The density protects their eggs and chicks from predatory gulls. While the egg would seem vulnerable to rolling off the edge, this does not usually happen. It has been suggested that the egg might simply spin if disturbed, or roll in an arc preventing it from falling over the cliff edge, but there is no evidence for either explanation. Ornithologist Tim Birkhead found that a pyriform egg placed experimentally on a steep slope did not roll, while a less pointed and more ellipsoidal egg did. He attributed the egg's stability to its long straight edge resting on the ground, creating more friction and making it less likely to move and fall. Guillemot chicks are born on rocky cliffs near the seaside. They leave the nest by jumping off the cliffsides before their wings are strong enough to allow them to fly, so they parachute down toward the ground as opposed to flying. Their dense, downy feathers and underdeveloped wings allow them to avoid serious harm when falling to the ground, so they bounce around slightly after hitting the ground. The name is ultimately onomatopoeic from the loud, high-pitched 'will, willem' begging calls of the newly fledged young of the common guillemot. The American name murre is onomatopoeic of the growling call of adult common guillemots.
Reader's Guide
Guillemots are significant in ornithology for their unique reproductive adaptations, particularly the pyriform egg that resists rolling off narrow cliff ledges, a feature that has been studied experimentally. Their dense breeding colonies on cliffs are a classic example of colonial nesting behavior, where high density itself provides protection from predators. The eggs were historically collected by men scaling cliffs on Scotland's St Kilda islands until the late 1920s, buried in peat ash, and eaten through winter, being considered similar to duck eggs in taste and nutrition. The genus Uria includes the common murre and thick-billed murre, while Cepphus includes the black, pigeon, and spectacled guillemots. Fossil records show prehistoric species of both genera, with Uria brodkorbi being the only known occurrence of the Alcini tribe in the temperate to subtropical Pacific. The etymology of the name reflects onomatopoeic origins from chick and adult calls, illustrating how common names can derive from bird vocalizations.
Did You Know?
- Guillemot eggs are large, around 11% of female weight, and pyriform (pear-shaped).
- Guillemot chicks leave the nest by jumping off cliffs before their wings are strong enough to fly, bouncing on landing.
- The name 'guillemot' is ultimately onomatopoeic from the begging calls of newly fledged young.
- Guillemot eggs were collected until the late 1920s on Scotland's St Kilda islands and eaten through winter.
Frequently Asked Questions
Who is Guillemot?
Guillemot is the shared common name for five seabird species in the auk family (Alcidae), belonging to the genera Uria and Cepphus. European usage includes both genera under the name, whereas North American usage restricts it to Cepphus only.
What are Guillemot's signature traits?
Guillemots are best recognized for their distinctive pear-shaped eggs and for forming extraordinarily dense colonies on sea cliffs. Each egg weighs roughly 11% of the female's body mass, an impressive ratio for a seabird.
How does Guillemot's breeding season end?
Once the single chick has fledged, the pair departs the cliff face and returns to open-ocean feeding grounds for the remainder of the year. The colony site is left unoccupied until the next spring arrival.
Why is Guillemot ecologically important?
Guillemots function as barometers of marine ecosystem health because their reproductive success closely mirrors the abundance of small fish and invertebrates in their foraging range. Their tightly packed cliff colonies also make them highly visible to predators and to environmental threats like oil spills.
How many Guillemot species exist?
Five living species are currently recognized: two in the genus Uria (common and thick-billed) and three in Cepphus (black, marbled, and rock guillemot).
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