The Bald Eagle is a huge bird, noticeably larger than a vulture, and twice the size of a Red-tailed Hawk. Although size is difficult to determine on birds in the field, eagles look large regardless of how far away they are, even birds from the southern population, which are smaller than the birds in the north. Adult Bald Eagles are perhaps the most well known raptor in the world. Birders and non-birders are familiar with their characteristic white head and tail, especially in the U.S. where it is the nation's symbol.
Bald Eagles prey mostly on fish, and are typically found near water, moving south if their local streams or lakes freeze over. They are extremely efficient at plucking fish from shallow waters in one fell swoop, missing much less often than the similar Osprey. They are also quite agile and capable of capturing ducks and other birds in flight. Despite their reputation as a fierce predator, Bald Eagles often scavenge dead animals, or steal prey from other raptors when the opportunity arises. This is frustrating for any Osprey that happens to nest near a Bald Eagle, who will steal fish from the Osprey all summer long.
Bald Eagles build massive stick nests in the tops of large trees, and in some cases on man-made structures and platforms. They add to their nests every year; some older nests reach such a weight that the tree supporting it collapses! Bald Eagles are communal during winter, when hundreds and even thousands may gather at food source and roost together in large snags each night. Females are notably larger than males, and this is most obvious when a pair is side-by-side. Bald Eagles have a relatively weak voice, conveying a series of high-pitched, descending whistles when agitated or courting.
In flight, Bald Eagles show long, somewhat broad wings.
The head is large and protruding, obviously more so than the similarly shaped Golden Eagle.
The wings appear to lack any bulge, whereas juveniles and 2nd-year birds are broader.
Appear slow moving and steady in flight.
Soar in wide circles with flat, or slightly raised, wings, and glide on slightly drooped wings.
In direct flight, display powerful, stiff, wing beats with deep upstrokes.
Adults have a gleaming white head and tail, blackish body, and yellow bill and eyes. Male and female of all ages are identical in plumage.
Juveniles are brownish overall with dark eyes and bill, and white on the underwing coverts, wing pits, and some secondaries. Tail is black with degrees of white mottling. Upper parts are blackish overall with slightly browner upperwing coverts, appearing two-toned overall.
2nd-year birds typically have a white belly and upperback, and a dusky bill with hints of yellow at the base. The eyes are still mostly dark.
3rd-year birds are similar to 2nd-years but eyes and bill more yellow. Typically have white speckled bellies. White on back is less prominent than on 2nd-years, but the white on the head is more prominent. 3rd-year birds have adult-shaped wings.
4th-year birds are variable in plumage, appearing adult-like but with signs of immaturity, such as dark flecking in the head and a dark tail tip, and leftover white mottling on the body and/or underwings. Most 4th-year birds have a dark eye-line like an Osprey.
5th-year birds are nearly identical to adults but with a few dark specks on the head, black tips on a few tail feathers, and a few white spots on the wing pits. Some 5th –years can't be told from full adults in the field.
Northern populations are migratory mainly from February through May (spring), and September through December (fall).
Adults may not migrate if there is open water with plenty of food throughout the winter months.
Southern populations are largely resident, but southern fledglings disperse north reaching the Chesapeake Bay region and Great Lakes during mid-May to mid-June.
(Map from Cornell Lab of Ornithology's All About Birds. For dynamic distribution maps, visit the eBird website.)