Adult males are large, dark brown above, and white below; the head is white with a black streak through each eye. Eyes are vivid yellow. Females usually have dark streaks on the breast whereas the males are usually clear white. Immatures are like adults except that their upper parts are flecked with white.
In flight, viewed from below, osprey are mainly white, with dark speckles on the breast, barring on the wings and tail, and a dark patch visible at the bend of each wing; the wings are characteristically angled, resembling an M. Viewed from head on, the wings are arched (something like a gull's), the bend of the wing held higher than the wing tips. Wings are long in proportion to the body size, and wing beats are typically slow and deep. Voice includes descending chirps and rising squeals, and a loud, clear whistle, often in a series and sometimes in response to other osprey.