There are two types of skuas seen in the oceans surrounding North America. The larger of the two skuas is the Great Skua, which is a stocky brown plumaged seabird that can be found far out at sea, mostly in the northern ocean waters. The South Polar Skua, as the name suggests, is more commonly found in the southern regions of the Atlantic and Pacific ocean.
The skuas are predators, much the same as jaegers and gulls, but are the largest and most aggressive of the group. These ocean birds are capable of catching and killing birds as large as shearwaters. Being predators, they are opportunists and mostly seek out smaller prey, sick or injured birds.
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.