Thursday, April 30, 2009

Osprey in New Jersey

ospreyOsprey, Sandy Hook - photo by Brian Richards

The osprey (Pandion haliaetus)) is a large raptor (bird of prey) usually seen near bodies of water that support adequate fish populations. In the 1800s, there was an abundant breeding population of osprey along the New Jersey coast and near most fresh water bodies.

Pesticide contamination and habitat loss gradually reduced the annual number of osprey nesting pairs throughout this past century. In fact, osprey populations plummeted from 500 pairs in the 1950s to 68 pairs in 1975. The species became one of the first to be included on the New Jersey Endangered Species List.

The osprey has a wingspan of 4.5 – 6 feet. It glides with its long, narrow wings pulled towards the body and, when viewed from the ground, resembles the shape of the letter "M".

They feed on fish and inhabit coastal rivers, marshes and bays, as well as rivers, lakes and reservoirs. They are known for their feet-first plunge into the water to catch their prey with their talons that have spines on them to pierce the fish's skin.

Ospreys nest on live or dead trees, manmade nesting platforms, light poles, channel markers and other elevated structures that offer an unobstructed view of the landscape near and around a water body.

Historically, the number of reproductive osprey pairs began to decline in the 1900s due to habitat loss, the eradication of nest trees, egg collecting and shooting. This was compounded by increased human settlement along the coast later in the century.

Between 1946 through 1964, the pesticide DDT was introduced into the environment to combat mosquitoes. It entered the food chain and eventually contaminated predators like the osprey. The chemical did not kill the birds as people often believe, but weakened the thickness of osprey eggshells, which would break under the weight of the bird during incubation. They can experience reproductive failure over a long period of time because DDT contamination can remain in an adult osprey's body for years.

Starting in 1979, the Endangered and Nongame Species Program transplanted eggs from healthy nests in the Chesapeake Bay area into New Jersey nests. Program staff also erected nesting platforms and began annual surveys to monitor osprey productivity.

The state's osprey population began to recover as nesting success improved and the number of nesting pairs increased each year.

Due to its improved reproductive success, its acceptance of manmade nesting structures and the decline of persistent pesticides, the status of the osprey in New Jersey was changed from endangered to threatened in 1985. They were the first species to be removed from the list.

Department biologists and volunteers counted 340 nests in 2001 and banded 201 young osprey in their nests in 2002.

The state currently conducts an aerial survey of the state's osprey population every two years. They observe nests yearly and band many of the young osprey chicks while they are still in the nest.

The Osprey Project in New Jersey reported that 38 new nest structures were erected or discovered in 2008: more than half (21) were occupied, and fourteen produced 25 young.

In typical fashion for NJ (and the East), most ospreys nested on man-made single-post structures (77%) and channel markers (5%), while only a few nested on antiquated 4-post nest platforms (3%). The occurrence of ospreys nesting on cell towers (1%) fluctuates from year to year, but that’s a structure favored by inland-nesting ospreys. Other nests can be found on transmission towers (3%), duck blinds (3%), and in dead trees (2%).

Ospreys get very creative in areas of the state where nest platforms are limited. They will try to build nests on many different structures including lighting poles on sports fields, weather stations, telephone poles,cranes, houses, and almost anything tall and stable.

The NJDEP works closely with the Conserve Wildlife Foundation of NJ (CWF) to use private donations to fund nest platform and habitat restoration projects along the Atlantic Coast. In the last three years, over forty nest platforms have been built and installed with private donations to CWF.

The next statewide census is scheduled for this year and will attempt to count all active nests during aerial and ground surveys.

NJDEP species information for the osprey (PDF)

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