There are two races or sub-species of the Iceland Gull. These are the Iceland Gull (Thayer's), most recently losing its status as a species of its own, being now recognized as a race of the Iceland Gull. It is known to nest in the central regions of the arctic and spend its winter months along the Pacific coast. The other is the Iceland Gull (Kumlien's), which nests in the eastern arctic islands and on Greenland. These gulls are more likely to be seen in the winter months in the surrounding waters of St. John's, Newfoundland and Labrador.
The Iceland Gull is a member of the white-winged gulls. Gulls that are more likely to be seen in the north, where there is snow and ice. These hardy gulls are often seen in the company of the Glaucous Gull in eastern North America, and the Glaucous-winged Gull found in the western areas of the continent.
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.