Population
It is estimated that there are approximately 2,000 pairs (active nests) on Long Island. The densest population is on eastern Long Island, known for its shallow bays, creeks, and private islands (Gardiners, Plum, Robins), allowing for excellent fishing and protected nesting sites.

Migration
Ospreys are a migratory bird that annually arrive on Long Island beginning in early/mid March from their wintering grounds in South America. Satellite tracking of individual Long Island birds (with lightweight “backpack” transmitters) show that they head to Venezuela and northern Brazil, with all departing our region by late October. A true harbinger of spring, the osprey’s arrival to our region coincides with winter melting away and the “running” of menhaden, or bunker fish, swimming from the ocean to the shallow bays and creeks to breed. These fish are the main component of the ospreys’ diet when they arrive in early spring.

Diet
Nearly 100% of their diet is fish – both fresh and salt water varieties. In the rare instances where fish are scarce, the “fish hawk” has been known to hunt small mammals, birds, snakes and lizards.
Nesting

• Historically ospreys would nest near the water in dead trees. Now ospreys often choose other high spots such as telephone and utility poles, which poses serious safety concerns for both the birds and our customers.
• If successful the previous season, adult birds nearly always return to their old nest sites. Males typically arrive a few days to a week before their mate to defend the site and make initial nest site improvements.
• Nests tend to be located in proximity to water help protect osprey from predators, such as foxes, raccoons, feral cats and even humans. However, in some cases, nests have been observed in fields and forests up to 5 miles from any open water.
• With both male and female helping during the peak of construction, more than 100 trips per day are common to retrieve nest material. Most of the material is within sight of the nest and while the male often collects more, the female does most of the final arranging and building.
• The nest has two components: The large sticks on the outside to provide shape and depth, and the soft lining of kelp strands, mats of seaweed, and bunches of grass. While osprey pairs have been known to build (and rebuild) a nest in a single day, it often takes 3-4 days for nest completion.
• Known as a “pack rat” species, ospreys collect corn stalks , nautical rope, fishing line, dog toys, plastic bags, rubber bands, broken garden tools, and many other items along the shoreline. This is most likely to help provide stability to the nest, rather than a unique decorating flair.
• Large nests can exist for decades and over time are used by several different pairs and generations. Several nest platforms placed by conservation groups in the late 1980’s still exist on parts of eastern Long Island today.

 
Mating

• As with all birds of prey, the females are often larger than the males – some females have wingspans approaching 5 feet, and weigh up to 4 pounds; males weigh in at 2 pounds. They have a characteristic black stripe through the eye and have charcoal and white feathers. In youth the eye is orange; in adulthood it becomes yellow. Ospreys mature after two years of age.
• Ospreys often mate for life, which is true of most birds of prey. However, mates most often split up when nests are destroyed and a breeding season is lost. Also, a nest may become abandoned and the female will leave her mate if the male does not provide enough for food for her and the young.
• Most females will lay three eggs (weighing 2-3 oz.) a few weeks to a month after arriving from their northern journey. Incubation, which is nearly all by the female, takes 5-6 weeks before hatching occurs. By the time they are 30 days old, nestlings reach 70-80% of their total body weight. At six weeks, most birds are ready to fledge the nest.

 
Sometimes ospreys will leave an egg unattended. Short periods of time, even 15 or 30 minutes, may not have any impacts on the viability of an egg. Full incubation may not be occurring yet. The viability of an egg not attended to (being incubated) depends on a variety of factors, including temperature. Water and wind could soak and addle the egg(s) and make them sterile. Ospreys may abandon a nest completely due predators, people getting too close, or, uncommonly, if a mate dies or moves on.

History

• On Plum Island, off the eastern tip of the North Fork, a colony of several hundred nesting pairs flourished in the 1800s thanks to the protection of a local lighthouse keeper. Without human intrusion, this population nested directly on the ground and is considered the largest colony in the world
• Between 1950 and 1975, populations declined precipitously with estimates that nearly 90% were lost due to the persistent pesticide DDT. A side effect of the chemical was thinning of the eggshells causing the adult to crush its precious treasure below it. As a result, ospreys nearly became extinct in New York State.
• After DDT was banned in 1972, the species began to recover and it became apparent that sufficient and viable nest sites did not exist. Once prone to nesting in dead trees or on remote islands, ospreys began to use telephone poles, utility poles and towers, abandoned buildings and other structures that that offered increased nesting opportunities but also came with increased risks and hazards. Conservation groups began erecting specially designed poles and platforms, which eventually led to the successful recovery of the birds on Long Island.
• Ospreys are not currently a threatened or endangered species, however they are protected by the Federal Migratory Bird Act and regulated by the U.S. Fish & Wildlife Service. The New York State Department of Environmental Conservation (DEC) is charged with regulatory enforcement of this law.

 
Distribution
Considered a cosmopolitan migratory species, ospreys are found on 6 of the 7 continents (except Antarctica). Breeding birds of North America winter in Central and South America, likewise nesting birds in Europe fly to Africa for a winter retreat.