Western Gull - NOT

[Steven Mlodinow]

Greetings All

So, being able to sit on a comfy chair and dissect marks one by one, the "apparent Western Gull" at Larimer Landfill is apparently not a Western Gull. Believe it or not, it is likely a LBBG. We (mostly me error) were misled by the bird's obvious secondary skirt (see Sibley for definition), a mark that is supposed to be present only on large Pacific gulls such as GW, Western, SB Gulls. Herring and LBB Gulls should not have such. Also, the bird seemed suitably big and big billed. However, plumage details point towards a LBB Gull with minimal white on tail (which was also misleading). 

Best Wishes

Steve Mlodinow