Age: The primaries are 1st generation, as are the brown median/lesser coverts and tertials. It's also likely the greater coverts are 1st generation, and the different color here is due to a combination of a paler pattern on this tract and wear. The gray scapulars are likely a mix of 1st alternate and formative feathers. Note also hints of a black distal tailband just below the primaries. Thus, we will assume this is a 1st cycle, but May-June is prime time for the start of flight feather molt, and only an open wing would reveal if the 2nd plumage cycle has "formally" commenced.
Identification: This is a small tern-like gull. The petite bill and short tarsi suggest the smallest of the sternine gulls. The black cap can be found on Bonaparte's at this time of year, but this head pattern, along with the solid brown covert band across the wing panel supports a different species. The black and white saw-tooth pattern on the primaries readily identifies this individual as a Little Gull.