I photographed this juvenile Least Sandpiper
at Village Creek, Fort Worth, Texas on September 8th, 1999; note
the reduced dark pattern in the lore, which is completely "broken"
near the eye:
the forecrown lightens but seems to just about meet the loral
lines at the base of the bill, separating the supercilia:
I this view with a Western Sandpiper, the lore on the right side
can just about be seen to match that on the left side:
I saw no pale at the base of the bill on this bird, and the pattern
of the coverts in general and especially the notched edge to the
innermost greater covert all point to this being a Least Sandpiper.