An auk is a bird of the family Alcidae in the order Charadriiformes. Extant
auks range in size from the least auklet, at 85 g and 15 cm, to the
thick-billed murre, at 1 kg and 45 cm. They are good swimmers and divers, but
their walking appears clumsy. Modern auks can fly. Due to their short wings,
auks have to flap their wings very quickly in order to fly.
Auks are superficially similar to penguins having black-and-white colours,
upright posture and some of their habits. Nevertheless, they are not
closely related to penguins, but rather are believed to be an example of
moderate convergent evolution. Auks live on the open sea and only go
ashore for breeding, although some species, like the common guillemot,
spend a great part of the year defending their nesting spot from others.
Several species have different common names in Europe and North America. The
guillemots of Europe are murres in North America, if they occur in both
continents, and the little auk becomes the dovekie.
Some species, such as the Uria guillemots, nest in large colonies on
cliff edges; others, like the Cepphus guillemots, breed in small groups on
rocky coasts; and the puffins, auklets and some murrelets nest in burrows. All
species except the Brachyramphus murrelets are colonial.
Feeding and ecology The feeding behaviour of auks is often
compared to that of penguins; both groups are wing-propelled pursuit
divers. In the region where auks live, their only seabird competition is the
cormorants. In areas where the two groups feed on the same prey, the auks
tend to feed further offshore. Although not to the extent of penguins,
auks have largely sacrificed flight, and also mobility on land, in exchange for
swimming ability; their wings are a compromise between the best possible
design for diving and the bare minimum needed for flying. This varies by
subfamily, the Uria guillemots and murrelets being the most efficient under
the water, whereas the puffins and auklets are better adapted for flying
and walking. This reflects the type of prey taken: strong-swimming murres hunt
faster schooling fish, whereas auklets take slower moving krill. Time depth
recorders on auks have shown that they can dive as deep as 100 m in the case of
Uria guillemots, 40 m for the Cepphus guillemots and 30 m for the auklets.
Evolution and distribution Traditionally, the auks were believed to
be one of the earliest distinct charadriiform lineages due to their
characteristic morphology. However, genetic analyses have demonstrated that
these peculiarities are the product of strong natural selection instead: as
opposed to, for example, plovers, auks radically changed from a wading
shorebird to a diving seabird lifestyle. Thus, today, the auks are no longer
separated in their own suborder, but are considered part of the Lari suborder
which otherwise contains gulls and similar birds. Judging from genetic
data, their closest living relatives appear to be the skuas, with these two
lineages separating about 30 million years ago. Alternatively, auks may have
split off far earlier from the rest of the Lari and undergone strong
morphological, but slow genetic evolution, which would require a very
high evolutionary pressure, coupled with a long lifespan and slow reproduction.
The earliest unequivocal fossils of auks are from the late Eocene, some 35 mya.
The genus Miocepphus, is the earliest known from good specimens. Two very
fragmentary fossils are often assigned to the Alcidae, although this may not be
correct: Hydrotherikornis and Petralca. Most extant genera are known to exist
since the Late Miocene or Early Pliocene. Miocene fossils have been
found in both California and Maryland, but the greater diversity of fossils and
tribes in the Pacific leads most scientists to conclude that it was there
they first evolved, and it is in the Miocene Pacific that the first fossils
of extant genera are found. Early movement between the Pacific and the
Atlantic probably happened to the south, later movements across the Arctic Ocean.
The flightless subfamily Mancallinae, which was apparently restricted to the
Pacific coast of southern North America and became extinct in the Early
Pleistocene, is sometimes includes in the family Alcidae under some
definitions. One species, Miomancalla howardi, is the largest charadriiform of
all time. The extant auks are broken up into 2
main groups: the usually high-billed puffins and auklets, as opposed to the
more slender-billed murres and true auks, and the murrelets and guillemots.
The tribal arrangement was originally based on analyses of morphology and
ecology. mtDNA cytochrome b sequence and allozyme studies confirm these findings
except that the Synthliboramphus murrelets should be split into a
distinct tribe, as they appear more closely related to the Alcini – in any
case, assumption of a closer relationship between the former and the
true guillemots was only weakly supported by earlier studies.
Of the genera there are only a few species in each. This is probably a
product of the rather small geographic range of the family, and the periods of
glacial advance and retreat that have kept the populations on the move in a
narrow band of subarctic ocean. Today, as in the past, the auks are
restricted to cooler northern waters. Their ability to spread further south is
restricted as their prey hunting method, pursuit diving, becomes less efficient
in warmer waters. The speed at which small fish can swim doubles as the
temperature increases from 5 to 15 °C, with no corresponding increase in speed
for the bird. The southernmost auks, in California and Mexico, can survive there
because of cold upwellings. The current paucity of auks in the Atlantic,
compared to the Pacific is considered to be because of extinctions to the
Atlantic auks; the fossil record shows there were many more species in the
Atlantic during the Pliocene. Auks also tend to be restricted to continental
shelf waters and breed on few oceanic islands.
Hydotherikornis oregonus, the oldest purported alcid from the Eocene of
California, is actually a petrel and is reassigned to the tubenoses. A 2003
paper entitled "The Earliest North American Record of Auk From the Late
Eocene of Central Georgia" by Robert M. Chandler and Dennis Parmley of Georgia
College and State University reports a Late Eocene, wing-propelled diving, auk
from the Priabonain Stage of the Late Eocene. These sediments have been dated
through Chandronian NALMA {North American Land Mammal Age}, at an
estimate of 34.5 to 35.5 million years on the Eocene time scale for fossil
bearing sediments of the Clinchfield Formation, Gordon, Wilkinson County,
Georgia. Furthermore, the sediments containing this unabraided portion of a
left humerus are tropical or sub-tropical as evidenced by a wealth of
warm water shark teeth, palaeophied snake vertebrae and turtles.
Systematics Basal and incertae sedis
Miocepphus Subfamily Alcinae
Tribe Alcini – typical auks and murres Uria
Common murre or common guillemot, Uria aalge
Thick-billed murre or, Brünnich's guillemot, Uria lomvia
Alle Little auk or dovekie, Alle alle
Pinguinus Great auk, Pinguinus impennis
Alca Razorbill, Alca torda
Tribe Synthliboramphini – synthliboramphine murrelets
Synthliboramphus Scripps's murrelet, Synthliboramphus
scrippsi – formerly in S. hypoleucus Guadalupe murrelet, Synthliboramphus
hypoleucus – sometimes separated in Endomychura
Craveri's murrelet, Synthliboramphus craveri – sometimes separated in
Endomychura Ancient murrelet, Synthliboramphus
antiquus Japanese murrelet, Synthliboramphus
wumizusume Tribe Cepphini – true guillemots
Cepphus Black guillemot or tystie, Cepphus
grylle Pigeon guillemot, Cepphus columba
Kurile guillemot, Cepphus columba snowi Spectacled guillemot, Cepphus carbo
Tribe Brachyramphini – brachyramphine murrelets
Brachyramphus Marbled murrelet, Brachyramphus
marmoratus Long-billed murrelet Brachyramphus
perdix Kittlitz's murrelet, Brachyramphus
brevirostris Subfamily Fraterculinae
Tribe Aethiini – auklets Ptychoramphus
Cassin's auklet, Ptychoramphus aleuticus Aethia
Parakeet auklet, Aethia psittacula Crested auklet, Aethia cristatella
Whiskered auklet, Aethia pygmaea Least auklet, Aethia pusilla
Tribe Fraterculini – puffins Cerorhinca
Rhinoceros auklet, Cerorhinca monocerata Fratercula
Atlantic puffin, Fratercula arctica Horned puffin, Fratercula corniculata
Tufted puffin, Fratercula cirrhata Biodiversity of auks seems to have been
markedly higher during the Pliocene. See the genus accounts for prehistoric
species. See also
Kiviak, a traditional Inuit food from Greenland that is made of auks preserved
in seal skin Tradeoffs for locomotion in air and
water References
Further reading Collinson, Martin. "Splitting headaches?
Recent taxonomic changes affecting the British and Western Palaearctic lists".
Brit. Birds 99: 306–323. Gaston, Anthony & Jones, Ian: The Auks,
Alcidae. Oxford University Press, Oxford. ISBN 0-19-854032-9
Paton, T.A.; Baker, A.J.; Groth, J.G.; Barrowclough, G.F.. "RAG-1 sequences
resolve phylogenetic relationships within charadriiform birds". Mol. Phyl.
Evol. 29: 268–278. doi:10.1016/S1055-7903(03)00098-8. PMID
13678682. Diving Birds of North America, by Paul
Johnsgard