Thse two images are of a Least Sandpiperat Tule Lake, Corpus Christi, Nueces county, Texas on May 10, 2014. The first pic is the first view I got, and it immediately recalled one of the tell-tale features of alternate Sharp-tailed Sandpiper, namely the undertail coverts with lateral chevrons. I don't recall seeing this extent of lower flank/ventral marking on the underparts of a Least Sandpiper, nor did I find any images like this during a brief search of the Internet:
