This distinctive Least Sandpiper-type calidrid was photographed at Tule Lake, Corpus Christi, Texas on May 17, 2009:
Note the shortish bill, the black/white lines on the mantle/upper back, high-contrast streaking in the crown (with a partial split-supercilum), rounded pale spot above the anterior lores, extensive well-defined streaking across the chest and to a limited degree down the upper flanks, lack of a notch on the outer edge of the dark center of the innermost greater secondary covert (which is an alternative-aspect type feather):
Compare this individual to the typical-looking late-Spring Least Sandpiper to the right; note the crown/nape/mantle patterns, and the chest-sides:
This individual fed almost exclusively by turning its head strongly (at times almost horizontally) to one side; the 4 or 5 nearby typical LESAs fed with the bill mostly held somehat vertically, but occasionally one would "lean over" - but not to the same extent as this individual did habitually:
Note below that the bill is shorter than the middle toe in this comparison, even though the middle toe is not fully-straightened:
Update September 2019: It recently came to my attention that there is a difference in the shape of the dark markings in the greater coverts (innermost only??): blunt or squared on Least Sandpiper; more pointed on Long-toed Stint. As with almost all ID features, there are exceptions... However, I think that the pattern on this individual is better for Long-toed Stint than for Least Sandpiper (of course, that does not mean that is IS a Long-toed Stint):
