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Larus is a large genus of
seabirds to which most
gulls belong. It has a world-wide distribution, and many
of its species are abundant and well-known birds in their
ranges.
They are in general medium to large
birds, typically grey or white, often with black
markings on the head or wings. They have stout, longish
bills and webbed feet.
The taxonomy of the large gulls in the Herring and Lesser
Black-backed complex is very complicated,
different authorities recognising between two and eight
species.
The Larus gulls interbreed in a ring
around the arctic
A classic example of ring species is the Larus gulls
circumpolar species ring. The range of these gulls forms a
ring around the North Pole. The Herring gull, which lives
primarily in Great Britain, can breed with the American
Herring gull (living in North America), which can also breed
with the Vega Herring gull, which can breed with Birula's
gull, which can breed with Heuglin's gull, which can breed
with the Siberian lesser black-backed gull (all four of
these live across the top of Siberia), which can breed with
the Lesser Black-backed Gull back in Northern Europe,
including Great Britain. However, the Lesser Black-backed
gull and Herring gull are sufficiently different that they
cannot interbreed; thus the group of gulls forms a ring
species. A recent genetic study has shown that this example
is far more complicated than presented here. For more
information about this, see
"The herring gull complex is not a ring species", D
Liebers, P de Knijff, AJ Helbig, Biological Sciences,
2004 Volume 271.
References
Harrison, Peter (1988): Seabirds (2nd
ed.).
Christopher Helm, London
ISBN 0-7470-1410-8