Cassin's Auklet

Cassin's Auklet is one of the plainest of the North Pacific auks, showing a uniform, unadorned sooty-gray plumage without the colorful bills or facial plumes seen in many relatives. Its subdued coloration reflects a life spent largely nocturnal at the breeding colony and inconspicuous at sea.

• Body feathers are a fairly uniform sooty slate-gray above, becoming paler dusky gray on the belly and undertail
• Feathers lack bold patches, stripes, or plumes, distinguishing them from the more ornamented puffins and Rhinoceros Auklet
• A small pale spot near the base of the lower mandible is a bare-part feature rather than a plumage trait, but is a helpful field mark on the living bird
• Flight feathers are short and rounded, typical of small diving auks with whirring flight
• Tail feathers are short and squared, in keeping with the species' small, compact build

• Adults show fairly uniform sooty-gray upperparts and paler gray underparts year-round, with little seasonal change
• Juveniles are similar but slightly duller and browner overall
• Sexes are alike in plumage
• A complete molt occurs after breeding, with flight feathers replaced on a schedule that renders birds flightless for a period

Cassin's Auklets breed in burrows on offshore islands along the Pacific coast of North America, from Baja California north to Alaska, often in large colonies. Outside the breeding season they remain largely within nearshore and offshore waters of the North Pacific along the same general coastline, rarely wandering far from their breeding range.

This auklet feeds mainly on small planktonic crustaceans and other zooplankton, diving to pursue prey in productive coastal upwelling waters. It nests in burrows on offshore islands, typically visiting the colony only under cover of darkness to avoid predators. Its calls are harsh, creaking or chattering notes given at night around the breeding burrow.