|Herring Gull (1st cycle). Winthrop Harbor, IL. 14 Feb 2015.|
There are some features that make this bird interesting - or more interesting than many 1st winter Herrings. The all white head (bleached or alternate feathers?), all black bill and the sparsely marked bases to the outer rectrices were enough to give us pause.
But I'm convinced that everything on this individual is within range for Smithsonianus, having seen thousands of 1st cycles that in one way or another match all the "parts" that make up this bird. It's not unheard of for 1st winter Smiths to have an all black bill. It's not unheard of for 1st winter Smiths to have an all-white head, and it's not unheard of for 1st winter Smiths to show a similar tail pattern (albeit approaching an old-world feel...click here for a table of variable Smith tails).
Herring Gull is a variable beast, and when I look at birds like this I don't get a "wow-this-is-really-different" impression. The burden of proof for why this "can't" be an American Herring is high, and anyone who thinks of it otherwise would probably benefit from watching more Herrings in the field.