Bart, I like to look at the axillaries (black on the loon) if I can't see white on the upper wing. Common Loons also have large feet trailing behind. And if you are in St. Mary's County you would probably be 99% correct to call them all Common Loons! Good Birding, Patty Craig Dameron, St. Mary's County, MD pattycraig@mail.ameritel.net