The white on the underside of the tail and the eye-ring look like yellow-rumped warbler to me.
http://www.nejohnston.org/birds/2010/07 ... G_2372.jpg
Despite there being no visible yellow in your pic.
Not the best at gull ID but i'll give it a try. […]
Both of the birds are Western Sandpipers, I am pre[…]
Thanks for sharing these great photos!