Age: There are two generations of flight feathers seen here. The three outer primaries appear to be the juvenile (1st basic) feathers of a smaller hooded gull. This is also true for the secondaries with brown trailing edge. The 5-6 newer inner primaries are 2nd generation, and so we can be sure this bird is a 2nd cycle. Assuming this is a resident of the northern hemisphere, we might guess it's the boreal spring/summer.
Identification: This month's quiz isn't too bad if we narrow down our choices to a hooded gull with a moderate sized bill in proportion to the head, a dark trailing edge and narrow tailband. Black-headed and Bonaparte's are the top two contenders. Black-headed typically shows dark pigment on the underwing (all that's seen here is a shadow effect and no black). The all-black bill also points away from Black-headed and favors Bonaparte's. May's quiz bird is a relatively straight-forward one-year old Bonaparte's molting flight feathers.
Muskegon County, Michigan. May.