Secondary Feather

'Adult bald eagle secondary feathers are inner wing flight feathers attached to the ulna bone in the bird’s forearm, playing a key role in providing lift and control during flight. These feathers are shorter but broader than the primary feathers and are located just beneath them on the wing. In adult bald eagles, secondary feathers typically range from about 28 to 32 centimeters (11 to 12 inches) in length. They are generally dark in color, veering toward black, but lighten toward the base near the feather’s tip. The overall plumage of an adult bald eagle is dark brown with a distinctive white head and tail, and the secondary feathers contribute to the bird’s aerodynamic shape. Feather length remains relatively stable in adults, though individual feathers wear down over time and are replaced every 3–4 years through molting.