There are three types of native scoters seen in North America. These are the Black Scoter, the Surf Scoter and the White-winged Scoter. There is also one vagrant from Eurasia, called the Common Scoter, that shows up on the coastal waters from time to time. Once they change into their winter plumage, the scoters are very difficult to identify. The plumages all turn into a somewhat solid black, leaving only the facial features to determine the species. With practice and a bird guide, one can identify the scoter species by the shape of their bills and the amount and location of white showing.
All scoters nest in the northern regions of North America. The White-winged Scoter nests in the most southern regions, where they can be found on the prairie lakes. Scoters have very colourful large bills when they are in their breeding seasons. These colours will disappear once they return to their non-breeding plumage. All the scoter species will spend their winter months on the oceans and only return to nest in fresh water lakes in the spring.
Avibase - the world bird database This site provides the user with a complete list of bird species, broken down per country, or in the example of the US or Canada, per state and province. Here, bird species names are available in other languages, a great asset to be used as a translation of foreign bird names.
ABA - American Birding Association This site represents an organization that maintains official records of all birds species that have been proven to have been seen inside the perimeters of the North American Continent and the surrounding bodies of water. Regular revised versions are posted to keep the bird list current at all times. This is the list used by all serious birders over their lifetime. You may be aware of the movie called the "Big Year". It was with this list that all the competing birders used in an attempt to set a new record as to how many bird species that could be seen by an individual birder in one calendar year.
I hope you will take advantage of these suggested websites. I have used each of them, in one way or another, throughout the years in my quest to better identify and understand our fine feathered friends.