It is one of the smallest alcids, only the closely related Least Auklet being smaller.

They are often found with other Auklet species such as the Least Auklet.

It often breeds in mixed-species colonies with the Least Auklet, a smaller congener.

The Least Auklet (Aethia pusilla) is a seabird and the smallest species of auk.

Least Auklet (Aethia pusilla).

Unlike many auks, which are fed fish carried crosswise in the bill, chicks of the Least Auklet are fed copepods and other zooplankton from a sublingual pouch, as are other small auklets.

The Least Auklet (Aethia pusilla) is a seabird and the smallest species of auk.

Least Auklet (Aethia pusilla).

One study examining the influence of Norway Rats on the reproductive success of Least Auklets (Aethia pusilla) found that even though there wasn't much evidence for predation, the overall reproductive success of the colony decreased significantly due to rats disrupting adult auklets attempting to brood or provision young chicks.