Compare with a Short-billed Dowitcher, http://www.pbase.com/image/136579036 , photographed a few days earlier. This Long-billed has fewer marks overall on the breast, as they usually do in the Fall, since their marks wear off more easily than those of Short-billed. The marks on the sides of the Long-billed's breast are bars rather than spots (both species have bars on the flanks). The base underpart color of the Long-billed is more red, the Short-billed more orange. The Long-billed shows no primary projection beyond the tertials; the Short-billed has noticeable projection. The Long-billed has a plumper body overall than the Short-billed. Finally (not by itself a decisive mark) this Long-billed's bill is longer than this Short-billed's. The best-known distinguishing mark -- white patches on the underside of Short-billed vs. solid red background on Long-billed -- is not reliable in Fall migration when the birds are in molt.