There is continuing debate about the
taxonomic status of Kumlien's Gull, and some authorities
consider the Thayer's Gull to be the dark-mantled form of the
Iceland Gull, with Kumlien's Gull (variously treated as a
subspecies of either Thayer's or Iceland Gulls) as an
intermediate example, forming a cline rather than separate
species. The American Ornithologists' Union considered Thayer's
Gull a subspecies of American Herring Gull from 1917 until 1973,
when they determined it was a separate species from Herring
Gull. In the UK as the scientific name implies it is considered
to be closer to Iceland Gull.
There has been just one Kumlien's Gull
reported from S. Gloucestershire;
1996: (1)
On June 30th a 1st winter moulting to 2nd
summer was identified at Oldbury Power Station, it was present
for eighteen days and was last noted on July 17th. This
occurrence constitutes the first report of this form for S.
Gloucestershire. (John Martin, DH Payne, Keith Vinicombe)