Terns are seabirds in the family Sternidae, previously considered
a subfamily (Sterninae) of the gull family Laridae
. They form a lineage with the gulls and skimmers which in turn
is related to skuas and auks. Terns have a worldwide distribution.
Most terns were formerly treated as belonging to one large genus
Sterna, with the other genera being small.
However analysis of DNA sequences supports the splitting of Sterna
into several smaller genera (see list, below)
Many terns breeding in temperate zones are long-distance migrants,
and the Arctic Tern probably sees more daylight than any
other creature, as it migrates
from its northern breeding grounds to Antarctic waters.
They are, in general, medium to large birds, typically with grey
or white plumage, often with black markings on the head.
They have longish bills and webbed feet. They are lighter bodied
and more streamlined than gulls, and look elegant in flight
with long tails and long narrow wings. Terns in the genus Sterna
have deeply forked tails, those in Chlidonias and Larosterna
shallowly forked tails, while the noddies (genera Anous, Procelsterna,
Gygis) have unusual 'notched wedge' shaped tails,
the longest tail feathers being the middle-outer, not the central
nor the outermost.
Terns ranges in size from the Least Tern, at 42 g (1.5 oz) and 23
cm (9 inches), to the Caspian Tern, at 630 g (1.4 lbs)
and 53 cm (21 inches). They make harsh, single-note calls.
|Lesser Crested Tern
|Great Crested Tern
|Chinese Crested Tern
Aleuta-tern: Sterna aleutica - sterna kamtschatica
is a genus of terns in
the bird family Sternidae
. It used to encompass most "white"
but mtDNA sequence comparisons have recently determined that this
arrangement is paraphyletic.
It is now restricted to the typical large white terns occurring near-globally
in coastal regions.
Of those, 14 are listed below, under Latin as Sterna..
One Arctic Tern, ringed as a chick (not yet able to fly) on the Farne
Islands off the Northumberland coast in eastern
Great Britain in summer 1982, reached Melbourne, Australia in October
1982, a sea journey of over 22,000 km
(14,000 statute miles) in just three months from fledgingan
average of over 240 km per day, and one of the longest
journeys ever recorded for a bird.
The name marsh tern refers to terns of the genus Chlidonias, which
are typically found in freshwater marshes,
rather than coastal locations. There are four species.
, the "brown-backed terns", is a genus
of seabirds in the tern family. Although the genus was first described
in 1832 by Johann Georg Wagler the four species in the genus were
until recently retained in the larger genus Sterna,
the genus that most terns are in .
Three of the four species are tropical, and one has a sub-polar breeding
range. The Sooty Tern has a pan-tropical distribution;
the Bridled Tern also breeds across the Tropical Atlantic and Indian
Ocean but in the central Pacific it is replaced by the
Spectacled Tern. The Aleutian Tern breeds around Alaska and Siberia
but winters in the tropics around South East Asia.
Thalasseus, the crested terns, is a genus of six species of seabirds
in the tern family. Thalasseus signifies a "creature of the sea".
It has a worldwide distribution, and many of its species are abundant
and well-known birds in their ranges.
These large terns breed in very dense colonies on coasts and islands,
and exceptionally inland on suitable large freshwater lakes close
to the coast. They nest in a ground scrape.
Thalasseus terns feed by plunge-diving for fish, almost invariably
from the sea. They usually dive directly, and not from the
"stepped-hover" favoured by, for example, the Arctic Tern.
The offering of fish by the male to the female is part of the courtship.
These species have long thin sharp bills, usually a shade of yellow
or orange except in the Sandwich Tern where the bill is black
with a yellow tip in most subspecies. All species have a shaggy crest.
In winter, the Thalasseus terns' foreheads become white.