Marbled Murrelet vs Common Guillemot

In short

The Marbled Murrelet and Common Guillemot are both members of the alcid family but differ significantly in their nesting habits and appearance. The Marbled Murrelet is smaller and nests in coastal forests, while the Common Guillemot is larger and nests on cliffs. Key differences include size, bill shape, and plumage patterns.

Identification tips

• Size and Shape: Look for the smaller, more compact Marbled Murrelet compared to the larger, elongated Common Guillemot.
• Bill Shape: The Marbled Murrelet has a shorter, more delicate bill, while the Common Guillemot's bill is longer and thicker.
• Plumage: In breeding season, the Marbled Murrelet's mottled plumage contrasts with the Common Guillemot's stark black and white.
• Nesting Habits: Marbled Murrelets nest in trees, a unique behavior among alcids, while Common Guillemots nest on cliffs.

Size

The Marbled Murrelet is smaller and more compact than the Common Guillemot, which is larger and more elongated.

Plumage

Marbled Murrelets have a mottled brown and white plumage during the breeding season, while Common Guillemots are mostly black and white with a more uniform appearance. In non-breeding plumage, the Marbled Murrelet becomes paler and more uniform, but still retains some mottling.

Behaviour

Marbled Murrelets are known for their secretive behavior and elusive nests in forests, while Common Guillemots are more social and nest in large colonies on cliffs.

Habitat

Marbled Murrelets nest in coastal, older forests and are often seen near shorelines, whereas Common Guillemots are typically found on rocky sea cliffs and open ocean waters.

Voice

Vocalizations are not a primary distinguishing feature between these species in the field.