This flock of Bonaparte's Gulls has gulls in various stages of their life. August and September are generally the months when Bonaparte's Gulls molt from one stage of life to another. The Bonaparte's Gull obtains its adult-like plumage after one year.
The gull at the top in the first and third photos with the brownish plumage and darker bars across the wing is a juvenile Bonaparte's Gull. The next step is the 1st Winter Bonaparte's Gull. A good example of this stage is the gull on the bottom of the third photo. What distinguishes this as a 1st Winter gull is the fair amount of black on the gray wings and its dark ear-spot.
The next stage after after the 1st Winter is the 1st Summer. A good example of this 1st Summer stage is the gull in the middle of the first photo. This Bonaparte's Gull has a black hood mottled with white and a black tail. A nonbreeding adult Bonaparte's Gull is the middle gull in the fifth photo. This gull has the black ear-spot and all pale gray (no black) wings of the nonbreeding adult.
There do not in these photos seem to be gulls with the full black hood of the breeding Bonaparte's Gull, but their seem to be many which are in various stages of molting from breeding to nonbreeding plumage.
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