Blog # 426 How to Spot an Ospreys

 Fledgling female Osprey with a catfish, courtesy of Cindy and Karel Sedlacek.

The Osprey (Pandion haliaetus) is unmistakable when flying across Cayuga Lake with crooked-wings and when performing its spectacular plunge dive after fish. Yet this graceful apex predator is often confused with a few local look-alikes. 

AVIAN DOPPELGÄNGERS

Many birders have trouble identifying Ospreys in flight when they only get a glimpse of a moving bird without time to note field marks. Ospreys are often confused with bald eagles, red-tail hawks, and large gulls.

Second-year bald eagles are often mistaken for Ospreys, especially when they are testing out an Osprey nest early in the year. Depending on their position and the lighting, the eagle’s undersides can easily resemble that of an Osprey except for two features—the feet and wingspread. The eagle’s feet are bright yellow compared to the Osprey’s white feet with dark talons. More noticeable is the size difference between the species. Although the eagle is only a few pounds larger than the Osprey, the bald eagle has a massive 12 foot wingspan, double that of the Ospreys 5-6 foot wingspan. 

Second year bald eagles resemble Ospreys.

Red-tailed Hawk when backlit in flight., courtesy of Flicker.

Greater Black-backed Gull also soars with its wing in an “M” shape.

IDENTIFYING AN OSPREY IN FLIGHT

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

Ospreys use counter shading for camouflage in the air. Here are key field marks.

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: Ospreys have very long, rectangular wings and long legs for their body size. 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, appearing M-shaped when seen from below. 

3. Head Markings: Even from a distance, the white and dark-brown pattern on an 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 at the wrist of the wing. The density of the patch can vary and could be confused with that of the rough-legged hawk, but an Osprey's wings are generally darker than those of a hawk.

5. Secondary Feathers: Ospreys have strong barring on their secondary feathers that contrast with the paler inner wing. This type of barring can be common on many juvenile raptors, but adult Ospreys maintain theirs for life.

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. Juveniles may have a buff wash on the breast, but that color doesn't last long and can be hard to see from a distance. 

IDENTIFY 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 white with a dark brown bandit mask on the head. Patterns of brown-tipped feathers on the crown vary depending on the bird's posture.

2. Eyes: Mature Ospreys have piercing, bright yellow eyes with a dark pupil. Immature birds have darker orange-yellow eyes that gradually lighten due to hormonal changes at sexual maturity, starting 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 called 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. 

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

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. 

IDENTIFY A FEEDING OSPREY 

Osprey while feeding, courtesy of S. Keeze.

Unlike many raptors that with plumage camouflaged for consuming their prey in 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 emblematic of a juvenile. 

5. Feeding: Ospreys are piscivorous (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. 

DON’T BE FOOLED BY THE GEESE

In case you have not figured it out, the five “Canada Geese” sitting on the Rt. 90 utility line from Ledyard to Union springs are decoys placed by NYSEG. The purpose of these decoys is to deter Ospreys from nesting nearby. We shall soon see if it works. My money is on the Osprey. Canada Geese do not compete with Ospreys, although the geese occasionally attempt to settle in Osprey nests before the hawk’s return in the spring. The Ospreys easily reclaim their real estate upon their arrival, as the geese are likely considered nothing but pests by the hawk.

Eyes to the sky! 

Candace 

Candace E. Cornell 

Friends of Salt Point 

Cayuga Lake Osprey Network

Lansing, NY 

cec22@cornell.edu 

EYES ON OSPREYS