Wing pattern looks similar to Baird's Sandpiper in Sibley.
BD: Agree the bird in the background with wings spread is a Baird's (one of the birds of 565?), As you noted, the wing lacks a really distinct white wing stripe. The bird with wings spread in the foreground is a Least. The bird is smaller but also has a relatively dull wing pattern, more white in the tail. The view here obscures the difference in wing shape, Least short and rounded, Baird's long and pointed.