Adult Thayer's and Kumlien's Gulls at Ashbridges Bay in Toronto

Declan Troy and I found this Thayer's Gull at Ashbridges Bay in Toronto on 31 December 2016. The photos on this page show the two ends of the Iceland-Thayer's cline. The cut-off between species and subspecies is arbitrary.

We identified it as Thayer's based on these characters: good overall size compared to Herring; mantle shade same as Herring, blackish primaries approaching Herring, white tips in primaries not surrounded by black as in Herring; the amount of winter head streaking is typical of Thayer's Gull; and dark eyed. 31 December 2016.

Adult Kumlien's Gull compared to Herring. It has mid grey primaries and a darker yellow eye than Herring. 31 December 2016

Same adult Kumlien's as above

This bird is very close to being a glaucoides Iceland Gull from Greenland. It has pure white wingtips except for a small faint grey streak, which puts it at the glaucoides end of the cline. 31 December 2016.

This was a very pale gull that stood out on the dock for its paleness: pale mantle, pale eye, white primaries except for the palest grey in the primaries, another with strong glaucoides influence.