Willets fall into two sub-species, Eastern and Western. Easterns Winter in S. America and return in March, so in winter all we see are the Westerns on the Gulf coast. Above are two Easterns and a Western taken in July of 2014 out at Big Reef on Galveston Island’s eastern most tip. The non-breeding Western is farthest from the lens but still appears larger than the right most Eastern. Westerns are generally more neutral and over-all lighter in color. Note also the longer more slender bill, though it’s a subtle field mark and variations on these metrics abound. Easterns look a bit more slender and delicate at the neck and head. Since Westerns breed inland, seeing the patterned breeding plumage on gulf beach specimens also indicates the Eastern.
Very handy to see both races together for comparison. Makes ID a snap. I prepared this post to help train myself in IDing these two. I keep getting confused in the field!