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.