This submission applies only to the bird in the foreground. It was identified using several features in conjunction.

1. Its rotund body shape; even though it is bent over feeding, a Short-billed Dowitcher would have a smoother transition from the head to the back and would look less "hunchbacked".
2. When blown up, the image shows that the dowitcher is in the end stages of molt, but even the remaining older feathers show very little wear (compare to the bird in the middle), especially in the coverts. This means that this bird is molting its relatively young juvenile feathers into its winter plumage. The median coverts that do show wear along their edge lack internal markings, features that would be visible on the remaining feathers of a juvenile short-billed.
3. The tail on this individual is mostly black with thin white bars. On a Short-billed Dowitcher, the tail would have even black and white bars or more white than black in an uneven pattern (see the bird in the middle)

This description applies only to the bird in the middle. The one in the foreground is a Long-billed Dowitcher. When the picture is blown up, it is clear that many of the covert feathers are heavily worn, meaning this individual is an adult molting into winter plumage. Unfortunately, there doesn't appear to be enough of the alternate plumage feathers left to be used to make a confident ID, however, other features are apparent that do lend weight to this identification.

1. The supercillium is clearly arched in comparison to the generally straighter supercillium on Long-billed Dowitchers.
2. Its tail has broad, uneven white bands, a feature more consistent with Short-billed Dowitcher than Long-billed.
3. According to several references I've found, Short-billed Dowitchers tend to have slightly yellower legs and bases to their bills than Long-bills wich lean towards having slightly greener legs and bills bases. These features appear to be consistent on these birds.

I am of course open to any dissenting discussions.