Rhinoceros Auklet

The Rhinoceros Auklet, Cerorhinca monocerata, is a seabird of medium size, boasting a robust, orange/brown bill adorned with a distinctive horn-like extension in breeding adults. Its plumage is a contrast of dark upperparts and lighter underparts, with breeding adults featuring white plumes above the eyes and behind the bill. Males are marginally larger than females.

Identification Tips

To identify the Rhinoceros Auklet, look for its large, strong bill with a unique horn protruding from it during the breeding season. The bird's dark upperparts and paler underparts, along with white plumes on breeding adults, are key characteristics. The species exhibits sexual dimorphism, with males being approximately 10% heavier than females.

Habitat

This auk prefers nesting in burrows or natural caves and cavities, often on inclines which facilitate take-off due to their less adept flying abilities.

Distribution

The Rhinoceros Auklet is found across the North Pacific, with breeding ranges from California's Channel Islands to Alaska's Aleutian Islands in North America, and from Hokkaidō and Honshū in Japan to the Korean Peninsula and Sakhalin Island in Asia. During winter, they can be found both offshore and inshore, with some individuals migrating, particularly from October to April in pelagic California waters.

Behaviour

Breeding occurs in early summer, with both parents incubating a single egg. The chick is nocturnally fed with fish, a behavior likely evolved as a response to predation. The species is monogamous, with pair-mates migrating separately but synchronizing foraging upon return to the colony.

Breeding

The Rhinoceros Auklet nests in burrows or natural cavities, laying a single egg. Both parents share incubation duties over 30-35 days, and the semiprecocial chick is fed nightly for 35-45 days.

Diet and Feeding

The diet of the Rhinoceros Auklet varies by location but generally includes small fish, krill, and squid. They dive up to 57 meters deep and can remain submerged for up to 148 seconds to catch prey.

Conservation status

The Rhinoceros Auklet is currently listed as Least Concern on the IUCN Red List of Threatened Species.