I don't want to sound like a know it all, but who says that it's a herring gull? While the UK has herring gulls of a different subspecies, I know the subspecies that resides in the US quite well . The outer flight feathers don't have enough black to my eyes, but I could also be WRONG since that's a different subspecies??

The UK has Larus argentatus argenteus , while the US has Larus argentatus smithsonianus

http://www.birdguides.com/html/vidli...arus_canus.htm

" The Common Gull is most likely to be mistaken for a Herring Gull but notice that it is much smaller with altogether more delicate features, including the fine bill which lacks a red spot. It also has greenish legs and a darker grey back than most Herring Gulls. In flight the black in the primaries makes a more extensive wedge with bolder neater white blobs near the tips. Immature Common Gulls in flight have a conspicuous black wedge on the leading edge of the primaries "

After much google research I still am not convinced of either ID ;) The white on the wing tips of the adult COMMON gull is missing and the BLACK feathers in the tips seems too little for herring gull. herring gulls have 4 different winter(or summer) plumages by age, so this very well could be a 3rd year herring with fewer black wing tip feathers than usual ;)