There are four types of eiders in North America. The Common Eider, the largest in the group, has the largest range and is seen across the North and on the east and west coastlines. The King Eider is also seen across the North and on the two coastlines in the winter months. The Spectacled Eider and the Steller's Eider are eiders seen only in the northwestern regions of Canada and around the coast of Alaska.
The eiders adapt to the arctic regions and cold waters they live in. They have very fine plumage, known as eider down. These birds have some of the most colourful and contrasting plumage of all the birds in North America. Identified by their large bills, the King Eider is identified by its large bill which gives it a most unusual look, featuring an enlarged bill in breeding season.
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.