Bald eagles seek habitat with water nearby, large sturdy trees for nests that can weigh a ton, abundant fish and other wildlife, and few human disturbances. Ospreys are also attracted to good eagle habitat; they catch fish with powerful talons, though eagles sometimes steal their prey. In flight, bald eagles can be confused with ospreys and turkey vultures, but eagles soar and glide with their head far in front of level wings and get only their feet wet when fishing, ospreys hold their wings in a distinctive M-shape, flap more than soar, and often plunge fully into the water, and turkey vultures rock from side to side in flight. Bald eagles and ospreys, once seldom seen for many years in Pennsylvania, are reappearing because of protective laws, conservation strategies, and reintroduction programs after declines caused by pesticides and human predation, while habitat loss, especially loss of clean water and old-growth, is now the primary threat to their continued recovery. Eagles and ospreys migrate through Pennsylvania in April-May and August-October, while turkey vultures migrate in mid-March and usually remain until November or December. When perched and in flight, the three birds differ in size, markings, wingshape, and wingspan: eagles keep their wings level, vultures form a V-shape, and ospreys make an M-shape. Eagles and ospreys are adapted as aerial hunters with keen eyesight, grasping feet and talons, and sharp beaks, while turkey vultures are adapted for scavenging with featherless heads and feet suited more for walking than for carrying food to a nest.