Jake:
On Cape Cod there are a couple of ways that you can hunt Eider without using decoys, a blind, or even a boat. 1. As Ty states, if you are ON there food source (ie Mussel bed) or near it, and sit curled up with camo on the Eider will assume you are a rock and come into their food source. 2. there are a number of "beach points" at the entrances of various harbors or a few rocky outcrops that the Eider trade by on a regular basis either during the early season migration or as part of there routes to feeding areas. I have also simply wandered out onto tidal flats and when large strings of eider come, simply crouch down.. they will fly right over your head (literally about 5 feet over your head if you stay still).
The shooting is typically pass shooting, of course, so being a good shot and having a good dog are a must to prevent cripples (eiders are tough birds). I will utilize this hunting method when I only have a few hours to hunt before heading to work, or just to enjoy an easy (no boats, gear etc) early morning with my dog.
I will say that setting up decoys, blinds, boats etc is often far more productive and provides much better "decoying" bird shooting. I think that a lot of "shooting discipline" is required when pass shooting to prevent crippling ducks.
Hope this answered your question.
Jim O
