Ospreys are found on all the Earth’s continents except for Antarctica. Photo: Jason Zangari/Audubon Photography Awards

The Osprey (Pandion haliaetus) is a large fish-eating raptor with a 2-foot body and 6-foot  wingspan. It is almost exclusively a fish-eater, catching fish by plunging feet-first into the water to grab its prey. Preferred nest sites are in snags. However, with so many dead trees cut down due to safety concerns, Ospreys will adapt to other structures such as telephone poles, transmission towers, light  stanchions, and purpose-built nest platforms. They build large nests of sticks and other material.

Ospreys in Connecticut return from South America beginning in mid-March generally claiming the nest sites they used the year before. Males and females arrive with a few days of each other and reestablish their bond. Occasionally another Osprey will try to displace one of the pair and an aerial battle will ensue. The result is most often that the newcomer is chased away.

Ospreys in New England migrate along the east coast of the US through Florida and island-hop across the Caribbean Sea to winter in northern South America. Their migration north follows roughly the same route.

When the pair is settled, the old nest will be rebuilt or added to with sticks, seaweed and grasses, driftwood, bark, mud, and even dangerous decorations like balloons, rope, and fishing line and nets. Males bring the larger sticks, some as long as 3-4 feet. Females are more likely to bring the smaller items. For days the pair will push and pull the nest material around the nest until the sticks are securely in position. When they are satisfied they will form a nest cup of softer material in the center.

Throughout the nest building the male will bring the female fish both to prove that he will be able to supply food to growing chicks and to help her recover from the 3000-4000-mile migration from South America. During this time the pair will mate frequently. After several weeks the copulation rate will increase, an indication that egg-laying is near. 

A mature female Osprey will lay 2-3 eggs about the size of chicken eggs. She will incubate them for about five weeks. Photo: reclaimednj CC BY-NC-SA 2.0

A mature female Osprey will lay 2-3 eggs at two-day intervals. Incubation starts after the first egg is laid. The female does all of the incubation except for short intervals when she leaves the nest to eat fish that her mate brings her and to preen to keep her feathers in good shape. While she is off the eggs, her mate will attend them. After 5-6 weeks of incubation the eggs hatch. 

Ospreys generally carry fish head-first to lessen the drag. Photo: Benjamin Knoot / Audubon Photography Awards

For another 60 days the Osprey chicks will need increasing amounts of fish each day with the family consuming about six pounds when the young fledge. At first the female will tear off small pieces of the fish her mate has brought, feed them to her chicks, and eat the larger and less choice pieces herself. As the chicks grow, when she is not feeding them the female will watch them from a nearby perch. After 6-7 weeks the chicks will start exercising their wings at the nest edge, hopping up and down with beating wings, and finally at 7-8 weeks taking off for short flights. In just a few days, however, the young birds join their parents for flights around the nest area. 

The parents continue to feed the young Ospreys with the youngsters taking large fish pieces to nearby perches to eat. While they do not need as much food as they did when they were growing, they continue to consume large amounts to fatten up for their first migration.

Two or three weeks after the fledging, the female Osprey leaves for  South America, returning to the same wintering area that she used before. The male will continue to feed the juvenile Ospreys while they learn how to catch fish themselves. After several weeks, the male will begin migration to his area in South America leaving the juveniles to fend for themselves. By the end of October the juveniles will follow their parents south to find an area with plentiful fish. They will stay in South America for two or three years before returning north to make their first attempt at breeding.

According to DEEP, ”In the 1940s, the coastal zone between New York City and Boston supported an estimated 1,000 active Osprey nests.“ Development along the shore and DDT-caused weak eggshells reduced the number to around 150 in 1969; there were only nine active nests in Connecticut in 1974. Since the 1970s the banning of DDT in the US has resulted in an increase of Osprey populations. However, the use of pesticides in the wintering grounds is still a threat. Global climate change is another threat to Ospreys. Warming ocean waters results in changes in the fish populations that Osprey depend upon.

BirdLife International 2016. Pandion haliaetus. The IUCN Red List of Threatened Species 2016: e.T22694938A93478747. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22694938A93478747.en. Downloaded on 23 July 2019.

Ospreys are found on every continent except Antarctica. There are two subspecies of Osprey , Pandion haliaetus carolinensis, found in North America, and Pandion haliaetus haliaetus, found in the rest of the world.

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