Guillemot

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.