Ring-billed Gull

Gulls have always been tricky for me--it seems that they have more plumages than other birds (first/second/third year; juvenile, adult, breeding/non-breeding...) and, frankly, too many of them are white, black and shades of grey.  Heermann's Gull is probably my favourite simply because I have seen them only in breeding plumage when their bills are so red that you can't mistake them for any other gull.
I was pretty good at distinguishing Ring-billed and Herring Gull, too, as they were the ones I saw most in New Jersey.  They were frequently in mixed flocks and  I learned to distinguish them by size comparison (though I admit that I also used leg color despite my usual prejudice against color as an identification criterion).  The Herring Gulls were reliably larger than than the Ring-billeds, in fact they were generally the largest gull around.  Now, however I find myself with a new set of gulls: both Herring and Ring-billed Gulls are not our 'local' species anymore (though they do occur).  You can understand my joy, then, when the other day I saw this fellow--and immediately welcomed it as a long lost friend.  Sadly, this individual is probably not long for this world--he was definitely weak and sickly which allowed my husband to get to close with the camera--but nonetheless, he had the yellowish legs, the ring on the bill and--joy, oh bliss, I discovered that Ring-billed can maintain its position of 'smaller' gull when I compare it to our current local resident: Glaucous-winged Gull.  So, by default, Ring-billed has started me on the way to learning another gull...