Aethia is a genus of four small (85–300g) Endemism to the North Pacific Ocean, Bering Sea and Sea of Okhotsk and among some of North America's most abundant seabirds.
Taxonomy and evolution
The genus
Aethia occurs only in the
North Pacific and adjacent waters, mainly in the
Bering Sea region. Along with Cassin's auklet (
Ptychoramphus aleuticus) they comprise the
monophyly tribe Aethinii. Molecular work has not yet resolved the relationship between the
Aethia auklets, but the group is a
sister group to Cassin's auklet, which is, in turn, a sister group to the Fraterculine auks (
puffins and rhinoceros auklet).
The genus Aethia did not enter into widespread use until the 1960s.[Storer, R.W. 1960. Evolution of the diving birds. Proceedings of the International Ornithological Congress 12: 694–707.] Initially, the auklets were placed in Razorbill,[Linnaeus, C., 1758. Systema Naturae, 10th ed. Stockholm] but later reorganized into genera including: Simorhynchus,[Stejneger, L. 1885. Results of ornithological explorations in the Commander Islands and in Kamtschatka. Bulletin of the United States National Museum No. 29.] Phaleris and Cyclorhynchus.
Fossil record
The first undisputed auk
are from the middle
Miocene (15 million years ago).
The first
Aethia fossils date from the late
Miocene (8–13 million years ago)
and the four extant species likely diverged rapidly about 5 million years ago.
There are one or two fossil species which lived in the area of today's California during the Late Miocene: Aethia rossmoori Howard, 1968 (Monterrey Formation of Orange County), and an undescribed taxon tentatively placed in this genus.
From the Pliocene there are Aethia barnesi N. A. Smith, 2013 (San Mateo Formation of San Diego County, California, and Aethia storeri N. A. Smith, 2013 (San Mateo Formation of San Diego County, California.
Species
There are four species of
Aethia.
breeding auklets can be difficult because they nest in hidden crevices.
[Jones, I.L., 1992. Colony attendance of Least Auklets at St. Paul Island, Alaska: implications for population monitoring. Condor 94, 93–100.]
Distribution
Breeding season
Aethia auklets are endemic to the North
Pacific Ocean and Sea of Okhotsk with notable
colonies in the
Kuril Islands, Commander Islands, along the Kamchatka and Chukota Peninsulas. In
North America, large colonies are in the
Aleutian Islands (
Buldir,
Kiska,
Semisopochnoi and
Gareloi Island) to the Gulf of Alaska and north to the islands of the
Bering Sea (St. Lawrence Island,
Pribilof Islands, St. Matthew Island).
Auklets have a high site fidelity, at both the colony and crevice level, although there can be a high divorce rate of up to 33% in least and crested auklets when both mates survive.
Winter distribution
The Winter distribution of auklets is poorly known.
likely winter near to breeding colonies
[Williams, J.C., Byrd, G.V. and Konyukhov, N.B. 2003. Whiskered Auklets Aethia pygmaea, foxes, humans and how to right a wrong. Marine Ornithology 31:175-180.] and many were reported by Aleuts to winter in the general area.
[Murie, O.J. 1959. Fauna of the Aleutian Islands and Alaska Peninsula. North American Fauna 61:1-364.] Auklets from the northern Bering Sea must move further south because of
pack ice surrounding colonies during the winter.
Breeding
Auklets are typically very social and nest in dense colonies (
are more dispersed).
All have some form of facial ornamentation such as large crests (
Whiskered auklet and
), auricular plumes (all four species), and crested and whiskered auklets have a tangerine-scented odour
which may function in
mate choice or species recognition, although this requires more study.
All Aethia auklets lay one white egg in a natural crevice and incubate for 25–36 days,[Byrd, G.V., Renner, H.M. and Renner, M. 2005. Distribution patterns and population trends of breeding seabirds in the Aleutian Islands. Fisheries Oceanography 14:139-159.]
Diet
The auklets are mainly planktivores, eating a variety of calanoid
,
krill and other
such as
jellyfish and
Ctenophora. Winter diet has not been studied.
Threats and conservation
Because they nest in crevices, auklets are vulnerable to predation by
,
[Atkinson, I.A.E. 1985. The spread of commensal species of Rattus to oceanic islands and their effects on island avifaunas. In Moors, P.J. (eds.). 1985. Conservation of Island Birds. ICBP Technical Publication No. 3, Cambridge.] and have been extirpated from some islands that contained
introduced for farming.
[Bailey, E.P. 1993. Introduction of foxes to Alaskan islands - history, effects on avifauna, and eradication. Fish and Wildlife Series Resource Publication 193. United States Department of the Interior, Fish and Wildlife Service, Washington, DC.] Eradication of rats from Rat Island was completed in 2008 and 2009.
[U.S. Fish & Wildlife Service. 2007. Restoring wildlife habitat on Rat Island. Environmental Assessment, Alaska Maritime National Wildlife Refuge, Anchorage AK. 141pp]
The large colony at Sirius Point, Kiska, Alaska (perhaps the largest auklet colony in the world
