Being that we have a lot of younger and new to the sport members on here. With the question of is it a coot or a commorant (no offense stump), thought I would repost a great resource, ducks at a distance. Stump you did the right thing, you were not sure so you asked, no harm in that.
http://www.npwrc.usgs.gov/resource/bird ... /index.htm
Just click on the species and you can see wing pattern and such. Also a lot of places sell a pocket size version of this. If you are new to the sport or old please do us all a favor and learn how to ID ducks. There are a lot of things that will chap my hide while in the duck blind, there are very few that will cause me to pull up, ride over and have a chat with someone. One of those is shooting birds that are not target species. Duck hunters have a bad rap as it is, all we need is some peta nutt to film some young duck hunters out on the lake busting up some grebs or something. Learn to ID ducks and other birds at that.