There are no recognised subspecies of the crested auklet. In the spring crested auklet nest on the island. Species include murre, grebe, murrelet, gull, tern, loon, auklet, petrel and eagle. They are often found with other auklet species such as the least auklet. It is one of the smallest alcids, only the closely related least auklet being smaller. This scent is also found in whiskered auklet. The event happened in the late summer when the auklet chicks began to fledge. This introduction decimated the birds of the chain, particularly seabirds like the whiskered auklet. It often breeds in mixed-species colonies with the least auklet, a smaller congener. Like forehead crests, these features vary widely within auklet populations. The crested auklet can measure in length, in wingspan and weigh . The crested auklet is recognized primarily by two characteristics during the breeding season. Many are burrow-nesters, such as the rhinoceros auklet, ancient murrelet and tufted puffin. The whiskered auklet ("Aethia pygmaea") is a small seabird of the auk family. The Cassin's auklet population is the world's largest.