The Bald Eagle -- which became our national bird over Ben Franklin's protests (the turkey, he said, was a more respectable species) -- is a vanishing American. Although it once could be seen across the country, future generations might know it only on out equally vanishing dollar bills, Laycock warns us, if we continue our ecocidal ways. As early as the '40's a retired banker turned eagle-bander discovered that these birds under the influence of pesticides laid soft-shelled eggs which often either failed to hatch or cracked easily or produced monstrosities; although eagles have been protected birds since 1962, they're still killed massively by ranching interests, most efficiently by shooting from low flying airplanes. The book offers eagle-lore galore -- on mating, migrating, feeding; on eagle eyries and the eagle eye (""an eagle's vision is roughly that of a man looking through six power binoculars""); on Old Abe, a Yankee mascot who was present at Vicksburg, but nothing, surprisingly, about Roosevelt's Blue. Laycock, an editor for Audubon magazine, has scattered bird seed for ecologists and conservationists.