I don't think I have any group of pics that I've labeled and re-labeled than medium sized terns. I went back to the beach with the family again yesterday. There were 2 avocets and a turnstone in addition to the more usual stuff, but terns are starting to accumulate.
This Common Tern allowed a close approach and is still in pretty full breeding plumage though the bare parts colors are starting to fade.
This next one is well into the moult, with a white forehead and some darker gray in the carpal bar area. It obviously has lost a lot of color from the bill.