The following material is adapted with permission from a fact sheet produced by the Hawk Mountain Sanctuary in eastern Pennsylvania.
Although there are anecdotal reports of osprey catching mollusks, snakes, birds, and mammals, fish comprise more than 99% of the species’ diet. Unlike bald eagles, ospreys usually do not feed on carrion.
Most ospreys are opportunistic and feed on the most accessible, abundant, and appropriately sized fish available. The species is not designed for deep diving and most fish are caught at or near the surface. Ospreys usually search for their prey from the air. Doing so is more energetically costly than perch-hunting, but it enables ospreys to search for food across greater areas. Perch-hunting is more common in winter when individuals only need to feed themselves.
While hunting, ospreys fly slowly over the water and often hover briefly when scanning intently. When an osprey detects a fish, it tucks its wings and drops toward the water. While descending, the osprey uses its wings and tail to adjust its position. Ospreys plunge into the water feet-first with their legs and talons fully extended. After diving, ospreys rest for a moment on the water and secure their grip on their prey before taking off. Once airborne with a fish, ospreys place one foot in front of the other, and rearrange the fish so the head faces forward. A flexible outer toe allows them to carry fish with two talons securely placed on either side of their prey.
Hunting success depends on the age of the osprey, type of fish, and weather. Young ospreys are less proficient hunters than adults. Ospreys typically catch slow- moving, bottom-dwelling species and are least adept at capturing fast-moving fish. Hunting becomes more difficult in choppy and murky water. The presence of emergent and submerged vegetation also decreases hunting success.