Every year in early spring, gulls migrate thu and stop off at WRL spillway for a bit. Around this time of the year a few Franklin's gulls show up with their black heads. Some of them, like the 3 here, have a pink blush on their breast. This indicates that they are newly arrived from their rich marine wintering grounds off the west coast of South America where something in their diet gives them that pink glow. It changes back to white once they have been here awhile.
Ring Billed gull (Larus delawarensis)
Franklin's gull (Leucophaeus pipixcan)