When feeding the Dowitcher uses their long bill in the motion of a sewing machine needle, up and down. They usually stay for longer periods of time in one spot, as opposed to other shorebirds that wade and probe.
I believe this bird is the Long-billed, which has a bulkier body with a more rounded back and a longer bill.
Can be difficult to tell between the Long and Short billed Dowitcher.
Wolf Song Blog 