Thayer's Gull (thayeri)

(last update: January 22, 2013)

Amar Ayyash (USA)
Mars Muusse (Netherlands)

Cook-Inlet Gull glaucescens x smithsonianus 1st cycle (2CY), January 18 2010, Morro Bay, CA. Picture: Amar Ayyash.

Visit: Amar's Blog.

Glaucous-winged Gull frequently hybridizes with Western, Herring and Glacous Gull in a south to north manner, respectively, from Oregon to northern Alaska. Some places hold more Glaucous-winged hybrids than pure individuals. It is very common to come across GWGU X WEGU crosses, sometimes called Olympic Gull, and not uncommon to find GWGU X HERG hybrids. GWGU X HERG hybrids, sometimes called Cook-Inlet Gull, can be mistook for Thayer's Gull. Here is a large bird that superficially resembles Thayer's. The white edges to the primaries may suggest Thayer's but the size of this individual is much more telling. The upperparts are a bit more frosty than Thayer's and the bill is that of Herring - certainly not Glaucous-winged.

Some similarity to Thayer's Gull, but HYBRID GLAUCOUS-WINGED GULL X AMERICAN HERRING GULL larger overall with longer and stouter bill, but plumage can overlap with Thayer’s. Some presumed hybrids resemble Thayer’s closely and may be difficult to identify without known species for size and structure comparison, but most hybrids are bulkier with larger bills.