Clearly theres a few Dunlin, ,, the really short bodied ones where the back is lighter than the rather darker primary coverts , I wouldve called sanderlings , I would call the ones which have primary coverts about the same as the back color and darkish underwings semipalms... but to tell you the truth, the size of the individual birds in these pix ,,the varied angle and lighting of a flock , precludes a hard and fast ID .. But If someone has a better recipe for reading them in flight like this , I would be interested too.