Blog # 253 Identifying Ospreys

Ospreys are unique among birds and are the only member of its family, Pandionidae. In general, Ospreys appear dark chocolate brown when seen from above and white when seen from below and are whiter than most raptors. This fish-eating raptor can easily be confused with other hawks and eagles depending on their activity.

Male Osprey with field marks indicated, courtesy of S. Keeze.

A PERCHED OSPREY

A perched Osprey is easy to confuse with many brown hawks and eagles. Look for the following field marks to quickly identify Ospreys:

1. Crown: The Osprey's crown is pure, plain white with a dark brown band across the forehead. The crown varies depending on the bird's posture and size of the crow.

2. Eyes: Mature Ospreys have bright yellow, piercing eyes with a dark pupil. Immature birds have darker orange-yellow eyes that gradually lighten as they reach sexual maturity around 18 months of age.

3. Auriculars: A broad dark chocolate-brown stripe extends across the Osprey's auriculars. The stripe is slightly narrower at the eyes and widens toward the nape, connecting to the dark plumage of the upperparts. It’s often considered the Osprey’s bandit mask.

4. Bill: Ospreys have a strongly hooked bill suitable for tearing slippery fish. The bill is black and has a thick base, which contrasts with larger and yellow bills of all eagles.

5. Throat and Underparts: Ospreys have counter shaded plumage with white underparts, from the chin and throat to the undertail coverts. Some minor brown mottling may show around the base of the throat, but white is by far the dominant color to make it less visible from a fish’s perspective.

6. Upperparts: A mature Osprey has dark chocolate-brown upperparts with no wing bars, mottling, or other distinguishing markings. A juvenile Osprey, however, will have a buff or whitish edging to the feathers that can give it a scaly look.

7. Perch: Ospreys frequently perch in open areas near water with abundant fish. Dead trees, utility poles, and other sturdy perches are preferred. They do not perch on wires.

8. Feet: Ospreys are aggressive hunters and have thick, strong legs and feet with sharply curved, black talons. The legs and feet themselves are whitish-gray. Eagles have yellow counterparts.

Osprey field marks in flight, courtesy of S. Keeze.

AN OSPREY IN FLIGHT

Many birders have trouble identifying Ospreys in flight when they may only get a glimpse of a moving bird without time to note field marks. Ospreys are often confused with eagles or large gulls in flight. Ospreys use countershading for camouflage in the air with its dark wings and back, making it less noticeable from above them in the air and white

undersides to blend into the sky from below.

1. Primary Feathers: When soaring, an Osprey's primary feathers–the "fingertips" of the wings–have a wide splay that shows the individual feathers similar to those of eagles and vultures, even from great distances.

2. Wing Size and Shape: For their body size, Ospreys have very long, rectangular wings and long legs. While the shape of the wings can seem to vary depending on the bird's flight pattern, a soaring Osprey has relatively straight wings with a marked kink in their wings, making an M-shape when seen from below.

3. Head Markings: Even from a distance, the white and dark brown pattern on Osprey's head is distinct. Check that the dark brown auriculars stretch to the back of the head rather than pointing down the cheeks as they do for peregrine falcons and other raptors.

4. Wrist: Ospreys have a prominent dark patch right at the wrist of the wing. The density of the patch can vary and could be confused with the rough-legged hawk, but Osprey's wings are generally darker than the hawk's overall.

5. Secondary Feathers: Ospreys have strong barring on their secondary feathers that make those feathers look darker compared to the paler inner wing. This type of barring can be common on many juvenile raptors, but even mature Ospreys have it.

6. Tail: The Osprey's tail has the same dark barring that is seen on its secondary feathers. The barring can be harder to see when the tail is closed but is easily visible when the tail is fanned.

7. Body: Most of an Osprey's body is plain white, though some degree of brown speckling can be common at the base of an adult's throat, especially on females. Juvenile birds may have a buff wash on the breast, but that color doesn't last long and can be hard to see from a distance.

Osprey while feeding, courtesy of S. Keeze.

AN OSPREY EATING

Unlike many raptors that trap and feed on their prey wherein their plumage is camouflaged for a wooded environment, ospreys typically feed out in the open on exposed perches. Once again, field marks aid in the Osprey’s identification.

1. Posture: When a raptor is feeding, it often spreads its wings and hunches its shoulders in a posture called mantling. This helps hide its hard-won prey from other hungry predators. Because ospreys feed in the open on high perches, they do not hunch as frequently and may straighten up between bites to observe other predators around them. However, they commonly mantle their pray in their nests to keep the fish away from nestmates.

2. Head Markings: An osprey's dark-brown and white head markings, including its dark brown eye stripe or bandit mask, are always readily visible, even when the bird is feeding. The white crown is also distinct in this posture.

3. Eye Color: The bird in the photograph above is young and shows the orange-yellow eyes of juveniles. Their eyes turn bright yellow as they mature. Eye color is visible from a great distance and a good identifying field mark.

4. Underparts: While feeding, the Osprey’s pure-white underparts are easily seen. Note that in this photo the upperparts are scaled with buff-white edges, indicating a juvenile bird.

5. Feeding: Ospreys are piscivorous and feed exclusively on fish. They grasp the fish in their powerful talons. Males eat the fish’s head before giving the remainder to its mate in the nest.

6. Tail: An osprey's tail is barred with relatively wide alternating dark-brown and white stripes, easily seen when the bird is perched or feeding. A ragged tip of the tail indicates that the feathers are worn, often from dragging along the water while hunting.

LOOK ALIKES

Common Osprey look-alikes include second-year bald eagles, red-tail hawks, and large gulls, such as greater black-backed gulls.