This horn is only present in breeding adults, and like the elaborate sheath on the bill of puffins is shed every year.

The plumage is dark on top and paler below; breeding adults (both male and female) possess white plumes above the eyes and behind the bill.

The auklet nests in burrows dug into the soil, or in natural caves and cavities between 1 and 5 m deep.

The semiprecocial chick is then fed each night with a bill full of fish (in the manner of puffins) for 35–45 days.

The first record of the clade from the Atlantic Ocean was reported by Smith et al. (2007) and suggests that the biogeographic history of Cerorhinca is more complex than previously thought.

[10] The prominent horn on the bill of breeding rhinoceros auklet is one evolutionary byproduct of this behavior.

Several bird species are able to detect cues through UV light,[11] which supports the claim that this fluorescence is also meant for breeding purposes.