Rhinoceros Auklet

The Rhinoceros Auklet is a stocky, dusky-brown seabird of the North Pacific, related to puffins despite its plainer overall coloring. Its most distinctive feature, and the source of its name, is a pale, upright horn-like projection at the base of the bill that develops during the breeding season, alongside two thin white plume-like feather tufts extending back from the eyes and gape. Outside the breeding season, the horn and plumes are shed, and the bird takes on a simpler, unadorned brownish appearance.

Despite the elaborate breeding ornaments, Rhinoceros Auklets are largely nocturnal at their colonies, coming and going from burrows under cover of darkness to avoid predation by gulls and other aerial predators.

Key field marks

• Overall dusky brown-grey plumage
• Pale, upright horn on the base of the bill in breeding adults
• Thin white plume feathers behind the eye and along the gape in breeding season
• Stout, deep orange-yellow bill

Similar species

• Cassin's Auklet is smaller, plainer, and lacks the bill horn and facial plumes.
• Tufted Puffin shares a chunky, dark-bodied look but has a much larger, brightly colored bill and long golden head tufts rather than a horn.
• Non-breeding Rhinoceros Auklets lose their ornaments and can appear relatively nondescript, requiring attention to overall shape and bill structure for identification.

Rhinoceros Auklets breed in burrows on vegetated islands and coastal slopes around the North Pacific, from California north through British Columbia and Alaska, and across to Japan and the Russian Far East. They favor islands free of ground predators, where dense burrow colonies can form in suitable soil.

Outside the breeding season, birds disperse over nearshore and offshore North Pacific waters, with many wintering along the outer coasts of their breeding range or moving somewhat farther south.

Behavior

Adults visit their nesting colonies mainly at night to avoid predation by gulls, making the species largely nocturnal on land despite being active during the day at sea while foraging.

Voice

Low growling and moaning calls are given inside burrows; birds are generally silent at sea.

Feeding

Small schooling fish such as sand lance and anchovy, along with some invertebrates, are caught by pursuit-diving and carried back to the burrow crosswise in the bill, sometimes several at a time.

Nesting and breeding

Pairs dig long burrows, sometimes over a meter deep, in soft soil on breeding islands; a single egg is laid, and chicks are fed at night, fledging on their own after the parents cease provisioning.