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Osprey

Pandion haliaetus ORDER: ACCIPITRIFORMES FAMILY: PANDIONIDAE

IUCN Conservation Status: Least Concern

Unique among North American raptors for its diet of live fish and ability to dive into water to catch them, Ospreys are common sights soaring over shorelines, patrolling waterways, and standing on their huge stick nests, white heads gleaming. These large, rangy hawks do well around humans and have rebounded in numbers following the ban on the pesticide DDT. Hunting Ospreys are a picture of concentration, diving with feet outstretched and yellow eyes sighting straight along their talons.

Ospreys are Nesting

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At a GlanceHelp

Measurements
Both Sexes
Length
21.3–22.8 in
54–58 cm
Wingspan
59.1–70.9 in
150–180 cm
Weight
49.4–70.5 oz
1400–2000 g
Relative Size
Smaller than a Bald Eagle; larger and longer-winged than a Red-tailed Hawk.
Other Names
  • Balbuzard pêcheur (French)
  • Gavilán pescador (Spanish)

Cool Facts

  • An Osprey may log more than 160,000 migration miles during its 15-to-20-year lifetime. Scientists track Ospreys by strapping lightweight satellite transmitters to the birds’ backs. The devices pinpoint an Osprey's location to within a few hundred yards and last for 2-3 years. During 13 days in 2008, one Osprey flew 2,700 miles—from Martha's Vineyard, Massachusetts, to French Guiana, South America.
  • Ospreys are unusual among hawks in possessing a reversible outer toe that allows them to grasp with two toes in front and two behind. Barbed pads on the soles of the birds' feet help them grip slippery fish. When flying with prey, an Osprey lines up its catch head first for less wind resistance.
  • Ospreys are excellent anglers. Over several studies, Ospreys caught fish on at least 1 in every 4 dives, with success rates sometimes as high as 70 percent. The average time they spent hunting before making a catch was about 12 minutes—something to think about next time you throw your line in the water.
  • The Osprey readily builds its nest on manmade structures, such as telephone poles, channel markers, duck blinds, and nest platforms designed especially for it. Such platforms have become an important tool in reestablishing Ospreys in areas where they had disappeared. In some areas nests are placed almost exclusively on artificial structures.
  • Osprey eggs do not hatch all at once. Rather, the first chick emerges up to five days before the last one. The older hatchling dominates its younger siblings, and can monopolize the food brought by the parents. If food is abundant, chicks share meals in relative harmony; in times of scarcity, younger ones may starve to death.
  • The name "Osprey" made its first appearance around 1460, via the Medieval Latin phrase for "bird of prey" (avis prede). Some wordsmiths trace the name even further back, to the Latin for "bone-breaker"—ossifragus.
  • The oldest known Osprey was 25 years, 2 months old.

Habitat


Lake/Pond

Unable to dive to more than about three feet below the water's surface, Ospreys gravitate toward shallow fishing grounds, frequenting deep water only where fish school near the surface. Ospreys nest in a wide variety of locations, from Alaska to New England, Montana to Mexico, Carolina to California; their habitat includes almost any expanse of shallow, fish-filled water, including rivers, lakes, reservoirs, lagoons, swamps, and marshes. Whatever the location, Osprey nesting habitat must include an adequate supply of accessible fish within a maximum of about 12 miles of the nest; open, usually elevated nest sites free from predatory mammals such as raccoons, and a long enough ice-free season to allow the young to fledge.

Food


Fish

The Osprey is the only hawk on the continent that eats almost exclusively live fish. In North America, more than 80 species of live fresh- and saltwater fish account for 99 percent of the Osprey’s diet. Captured fish usually measure about 6–13 inches in length and weigh one-third to two-thirds of a pound. The largest catch on record weighed about 2.5 pounds. On very rare occasions, Ospreys have been observed feeding on fish carcasses or on birds, snakes, voles, squirrels, muskrats, and salamanders. Ospreys probably get most of the water they need from the flesh of their prey, although there are reports of adults drinking on hot days.

Nesting

Nesting Facts
Clutch Size
1–4 eggs
Number of Broods
1 broods
Egg Length
2.2–2.7 in
5.5–6.8 cm
Egg Width
1.7–2 in
4.2–5 cm
Incubation Period
36–42 days
Nestling Period
50–55 days
Egg Description
Cream to pinkish cinnamon; wreathed and spotted with reddish brown.
Condition at Hatching
Capable of limited motion. Covered with down and with eyes open.
Nest Description

Osprey nests are built of sticks and lined with bark, sod, grasses, vines, algae, or flotsam and jetsam. The male usually fetches most of the nesting material—sometimes breaking dead sticks off nearby trees as he flies past—and the female arranges it. Nests on artificial platforms, especially in a pair’s first season, are relatively small—less than 2.5 feet in diameter and 3–6 inches deep. After generations of adding to the nest year after year, Ospreys can end up with nests 10–13 feet deep and 3–6 feet in diameter—easily big enough for a human to sit in.

Nest Placement

Tree

Ospreys require nest sites in open surroundings for easy approach, with a wide, sturdy base and safety from ground predators (such as raccoons). Nests are usually built on snags, treetops, or crotches between large branches and trunks; on cliffs or human-built platforms. Usually the male finds the site before the female arrives.

Behavior


Aerial Dive

Adept at soaring and diving but not as maneuverable as other hawks, Ospreys keep to open areas, flying with stiff wingbeats in a steady, rowing motion. Primarily solitary birds, they usually roost alone or in small winter flocks of six to ten. Nesting Ospreys defend only the immediate area around their nest rather than a larger territory; they vigorously chase other Ospreys that encroach on their nesting areas. In breeding season, males perform an aerial "sky-dance," sometimes called "fish-flight." With dangling legs, often clasping a fish or nesting material in his talons, the male alternates periods of hovering with slow, shallow swoops as high as 600 feet or more above the nest site. Sustaining this display for 10 minutes or more, he utters repeated screaming calls while gradually descending in an undulating fashion to the nest.

Conservation

status via IUCN

Least Concern

Ospreys are a conservation success story and their populations grew by about 2.5 percent per year from 1966 to 2010, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 500,000 with 21 percent spending some part of the year in the U.S., 28 percent in Canada, and 3 percent in Mexico. They rate a 7 out of 20 on the Continental Concern Score and are not on the 2012 Watch List. The species' decline was halted by pesticide bans and the construction of artificial nest sites. Osprey numbers crashed in the early 1950s to 1970s, when pesticides poisoned the birds and thinned their eggshells. Along the coast between New York City and Boston, for example, about 90 percent of breeding pairs disappeared. Osprey studies provided key support for wider legal arguments against the use of persistent pesticides. After the 1972 U.S. DDT ban, populations rebounded, and the Osprey became a conservation success symbol. But Ospreys are still listed as endangered or threatened in some states—especially inland, where pesticides decimated or extirpated many populations. As natural nest sites have succumbed to tree removal and shoreline development, specially constructed nest platforms and other structures such as channel markers and utility poles have become vital to the Osprey’s recovery. Sadly, a growing cause of death for Ospreys is entanglement at the nest: the adults incorporate baling twine and other discarded lines into their nests; these can end up wrapped around a chick's feet and injure it or keep it from leaving the nest.

Credits

Range Map Help

Osprey Range Map
View dynamic map of eBird sightings

Migration

Resident to long-distance migrant. Most Ospreys that breed in North America migrate to Central and South America for the winter, with migration routes following broad swaths of the eastern, interior, and western U.S. A few Ospreys overwinter in the southernmost United States, including parts of Florida and California.

Backyard Tips

Consider putting up a nest platform to attract a breeding pair. Make sure you put it up well before breeding season. You'll find plans for building a nest structure of the appropriate size on our All About Birdhouses site.

Find This Bird

Near open water with an abundant supply of fish, listen for the Osprey’s whistling or chirping calls overhead, or look for this bird's distinctive flight profile and heavy wingbeats. From spring into fall, a boat or raft on a lake or river can provide an especially good vantage point. Scan treetops and other high spots along the shore for perched adults and untidy stick nests piled atop a platform, pole, or snag out in the open.

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