Of the 3 shorebird species that have such long narrow wings, Solitary, Buff-breasted and Baird's, this is the only brown backed of the group with such a plain underwing. Solitary Sandpipers are gray and white while the brown Buff-breasted has a distinct dark band at the carple area of the underwing coverts. With practice and reasonable looks, these 3 species with such swallow like flight, can be fairly easily IDed in flight by the underwing pattern.