The term "skein" is most commonly used to refer to a wound ball of yarn with a center pull strand. A less known use of the term "skein" is to describe the symmetric V shape flight formation of geese, ducks, and other migratory birds in flight. Most waterfowl fly at speeds of 40 to 60 mph at an altitude of 200 to 4,000 feet. Some migrate as much as 2,000 to 3,000 miles.