This circumpolar species is a very rare autumnal visitor to our shores. Its chief breeding-grounds are the Arctic regions of North America, whence it migrates southwards, in winter.
The adult has a slate grey back; the head and neck are very dark grey, tail and under parts white. In winter the forehead and crown are white. In their first autumn the young are ash grey on the occiput, nape, and back. The tail feathers have broad black tips. Length 13 in.; wing 10·75 in.
This species may always be recognised by the forked tail.
THE WEDGE-TAILED GULL
Rhodostethia rosea, Macgillivray
This extremely scarce Arctic Gull is said to have been obtained in Yorkshire on one occasion. It may be recognised by the wedge-shaped tail.
The adult is grey on the mantle; the rest of the plumage, except for a narrow black ring round the neck, is pure white. Length 13·5 in.; wing 10·25 in.
BONAPARTE’S GULL
Larus philadelphia (Ordigny)
This is a common North American species, of which some three examples have been taken in the United Kingdom.
In summer the adult has the head and neck black; mantle grey; tail and under parts white. The black on the head is lost in winter. Length 14 in.; wing 10·25 in.
This species may always be recognised by the white margins to the inner webs of the two outer primaries.