Hi Alastair
Alastair Carr wrote:
1. Thayer's Gull and Iceland Gull are considred, in this country, sub-species (at the moment). The hydrid being Kumlin's Gull. An excellent example is the Carrion and Hooded Crow.
:
The BOURC currently treat Thayer's as a subspecies of Iceland Gull, along with Kumlien's Gull. Whether Kumlien's Gull is the result of introgression of eastward-expanding populations of Thayer's Gull into Iceland's range is as yet unclear and more sampling at the colonies is required to understand the relationship between the three forms.
Alastair Carr wrote:
2. Thayer's Gull and Icelend Gull are seperate species. Kumlin's Gull is just a race of Iceland Gull.
:
The AOU currently treat Thayer's as a separate species and Kumlien's as a race of Iceland Gull. Recent molecular work has indicated that Thayer's and Iceland may not even be sister taxa.
Alastair Carr wrote:
The Big Questions - BBC One - Are Iceland Gull and Thayers Gull different species? Are Kumlin's Gull hybrids? 
dunno, you'll have to wait...
_________________
Dr Alexander C. Lees
Lecturer in tropical ecologyManchester Metropolitan University
Lab Associate
Cornell Lab of Ornithology,
Cornell University
http://www.freewebs.com/alexlees/index.htm@Alexander_Lees