Osprey numbers continue to rise!

by Ben Wurst, Habitat Program Manager

Three osprey nestlings were a common sight in many nests from Sedge Island to Little Egg Harbor, New Jersey. © Ben Wurst

Volunteers, CWF staff, and biologists with NJ Fish & Wildlife recently completed osprey nesting surveys throughout coastal areas of New Jersey. Each year these “osprey banders” complete “ground surveys” (referred to as ground surveys because they are surveying nests by land/sea, not by helicopter) that cover around 70% of the state population. I survey colonies on Barnegat Bay, Little Egg Harbor, and Absecon. The surveys are meant to keep track of the population and determine its health. During the surveys the banders access nesting areas mainly by boat since most ospreys nest in coastal areas or by water (their source of food). We use ladders to access nests where we count the number of young produced and then place an aluminum band on each of the young.  For the past two years we have also been collecting feather samples for a study being conducted by the Academy of Natural Sciences in Philadelphia where they are analyzing the stable isotopes to determine what ospreys are eating and how their diet has changed over time. More specifically they’ll be looking for changes in the isotope profiles across the local range of ospreys – something that has never been done before.

In one area, Sedge Island WMA, that I’ve surveyed for the past few years I surveyed 27 nests. 22 of those nests were occupied and produced a total of 47 young. 34 of those young were banded for future tracking. From the survey I can calculate the productivity or reproductive rate which is a measure of how healthy the population of that colony is. The productivity rate for Sedge Island is 2.14 young/active(known-outcome)nest this year which is the highest ever recorded (see chart at right for more details). These awesome results are the result of calm and mild weather conditions this spring and summer, high availability of prey, and possibly the increased amount of experienced breeding birds. Another factor that has surely helped to give the population a boost is the increased availability of suitable nest sites along the coast. Since 2004, I’ve helped to install more than 100 nesting platforms. Many of these platforms replaced old dilapidated structures and now give ospreys a better chance at successfully raising young that will eventually return to New Jersey to reproduce.

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