Osprey Information


Please thank Juan and Al for fixing the nesting platform by the pool for our Osprey!!  The birds are happy!!!

Ospreys are very large, distinctively shaped hawks. Despite their size, their bodies are slender, with long, narrow wings and long legs. Ospreys fly with a marked kink in their wings, making an M-shape when seen from below. Ospreys are brown above and white below, and overall they are whiter than most raptors. From below, the wings are mostly white with a prominent dark patch at the wrists. The head is white with a broad brown stripe through the eye. Juveniles have white spots on the back and buffy shading on the breast.

Ospreys search for fish by flying on steady wingbeats and bowed wings or circling high in the sky over relatively shallow water. They often hover briefly before diving, feet first, to grab a fish. You can often clearly see an Osprey’s catch in its talons as the bird carries it back to a nest or perch.

 

The osprey tolerates a wide variety of habitats, nesting in any location near a body of water providing an adequate food supply. It is found on all continents except Antarctica, although in South America it occurs only as a non-breeding migrant.

As its other common names suggest, the osprey’s diet consists almost exclusively of fish. It possesses specialised physical characteristics and exhibits unique behaviour to assist in hunting and catching prey. As a result of these unique characteristics, it has been given its own taxonomic genus, Pandion and family, Pandionidae. Three subspecies are usually recognized; one of the former subspecies, cristatus, has recently been given full species status and is referred to as the eastern osprey.

The osprey breeds near freshwater lakes and rivers, and sometimes on coastal brackish waters. Rocky outcrops just offshore are used in Rottnest Island off the coast of Western Australia, where there are 14 or so similar nesting sites of which five to seven are used in any one year. Many are renovated each season, and some have been used for 70 years. The nest is a large heap of sticks, driftwood, turf or seaweed built in forks of trees, rocky outcrops, utility poles, artificial platforms or offshore islets.[33][39] As wide as 2 meters and weighing about 135 kg, large nests on utility poles may be fire hazards and have caused power outages.

Generally, ospreys reach sexual maturity and begin breeding around the age of three to four, though in some regions with high osprey densities, such as Chesapeake Bay in the U.S., they may not start breeding until five to seven years old, and there may be a shortage of suitable tall structures. If there are no nesting sites available, young ospreys may be forced to delay breeding. To ease this problem, posts are sometimes erected to provide more sites suitable for nest building.  In some regions ospreys prefer transmission towers as nesting sites, e.g. in East Germany.

The platform design developed by one organization, Citizens United to Protect the Maurice River and Its Tributaries, Inc. has become the official design of the State of New Jersey, U.S. The platform plans and materials list, available online, have been utilized by people from a number of different geographical regions.  Osprey-watch.org is the global site for mapping osprey nest locations and logging observations on reproductive success.

Ospreys usually mate for life. Rarely, polyandry has been recorded. The breeding season varies according to latitude. In spring the pair begins a five-month period of partnership to raise their young. The female lays two to four eggswithin a month, and relies on the size of the nest to conserve heat. The eggs are whitish with bold splotches of reddish-brown and are about 6.2 cm × 4.5 cm (2.4 in × 1.8 in) and weigh about 65 g (2.3 oz).  The eggs are incubated for about 35–43 days to hatching.

The newly hatched chicks weigh only 50–60 g (1.8–2.1 oz), but fledge in 8–10 weeks. A study on Kangaroo Island, South Australia, had an average time between hatching and fledging of 69 days. The same study found an average of 0.66 young fledged per year per occupied territory, and 0.92 young fledged per year per active nest. Some 22% of surviving young either remained on the island or returned at maturity to join the breeding population. When food is scarce, the first chicks to hatch are most likely to survive. The typical lifespan is 7–10 years, though rarely individuals can grow to as old as 20–25 years.

The oldest European wild osprey on record lived to be over thirty years of age. In North America, great horned owls (Bubo virginianus), golden eagles (Aquila chrysaetos), and bald eagles (Haliaeetus leucocephalus) are the only major predators of ospreys, capable of taking both nestlings and adults.[36][47][48][49][50] However, kleptoparasitism by bald eagles, where the larger raptor steals the osprey’s catch, is more common than predation. The white-tailed eagle (Haliaeetus albicilla), which is very similar to the bald eagle, may harass or prey on the osprey in Eurasia.[51] Raccoons (Procyon lotor) can be a serious threat to nestlings or eggs if they can access the nest.[52] Endoparasitic trematodes (Scaphanocephalus expansus and Neodiplostomumspp.) have been recorded in wild ospreys.

A very distinctive fish-hawk, formerly classified with other hawks but now placed in a separate family of its own. Along coastlines, lakes, and rivers almost worldwide, the Osprey is often seen flying over the water, hovering, and then plunging feet-first to catch fish in its talons. After a successful strike, the bird rises heavily from the water and flies away, carrying the fish head-forward with its feet. Bald Eagles sometimes chase Ospreys and force them to drop their catch. In many regions, landowners put up poles near the water to attract nesting Ospreys.

Feeding Behavior

Flies slowly over water, pausing to hover when fish spotted below; if fish is close enough to surface, the Osprey plunges feet-first, grasping prey in its talons.

Eggs

3, sometimes 2-4. Creamy white, blotched with brown. Incubation is by both parents but mostly by female, about 38 days. Young: Female remains with young most of time at first, sheltering them from sun and rain; male brings fish, female feeds them to young. Age of young at first flight averages about 51-54 days. 1 brood per year.

Young

Female remains with young most of time at first, sheltering them from sun and rain; male brings fish, female feeds them to young. Age of young at first flight averages about 51-54 days. 1 brood per year.

Diet

Almost entirely fish. Typically feeds on fish 4-12″ long. Type of fish involved varies with region; concentrates on species common in each locale, such as flounder, smelt, mullet, bullhead, sucker, gizzard shad. Aside from fish, rarely eats small mammals, birds, or reptiles, perhaps mainly when fish are scarce.

Nesting

Courtship displays include pair circling high together; male may fly high and then dive repeatedly in vicinity of nest site, often carrying a fish or stick. Nest site is usually on top of large tree (often with dead or broken top) not far from water. Also nests on utility poles, duck blinds, other structures, including poles put up for them. May nest on ground on small islands, or on cliffs or giant cactus in western Mexico. Site typically very open to sky. Nest (built by both sexes) is bulky pile of sticks, lined with smaller materials. Birds may use same nest for years, adding material each year, so that nest becomes huge.

Migration

Some are permanent residents in southern Florida; migratory elsewhere. Migrants travel singly, not in flocks, often following coastlines, lake shores, rivers, or mountain ridges.

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