Friday, January 12, 2018

Eagles Across New Jersey

Bald Eagle in flight at Mountain Lakes Preserve
A bald eagle in flight at Mountain Lakes Preserve in Princeton, New Jersey.

Eagles are probably New Jersey's most successful comeback story when it comes to endangered species. But that doesn't mean that we can be complacent about that recovery.

Bald eagles have been removed from the federal endangered species list, although they are still protected by other federal laws. In New Jersey, eagles are still considered an endangered species during the breeding season, which runs from January through June. The rest of the year they fall under the threatened species category.

In Sussex County, for example, the number of chicks that fledged dropped this year from a year before. The number of known, observed, eagle nests also dropped. This information, according to the 2017 Bald Eagle Report issued by the NJ Division of Fish and Wildlife, shows a slight decrease in the number of eaglets that made that first flight was down slightly across the state. There were 216 last year and only 190 this year.

That drop is not catastrophic and may not continue in 2018.

Bald Eagle Fledgling 26 June 2013 New Jersey USA from Michael Black on Vimeo.
A New Jersey fledging before it has acquired its distinctive white "bald" head.

Mortality in chicks is usually due to adverse weather at critical times in the nesting period, and predation.

Bald eagles in NJ and across the country were much more common until the late 1950s when the population plummeted. Why? The main cause was human use of the pesticide DDT which had entered the food chain and caused female eagles to lay eggs with very thin shells, which did not survive incubation.

By the time DDT was banned in the U.S. in 1972, there was only one nesting pair of eagles in New Jersey.

Twenty years later, biologists throughout the Northeast were importing young eaglets that could be artificially raised (hacked) until they could fledge. Those young eagles would range in wide areas but generally will return to the area where they fledged to find a mate.

New Jersey had 23 nesting pairs by 2000, 48 pairs by 2005, 82 pairs by 2010 and 150 pairs by 2015.

Though the monitoring program is run by staff from the Division of Fish and Wildlife, most of the observations are done by volunteers. These devoted folks check assigned nests at least weekly, note when eggs are present, how many hatch and whether or not those young fledge.

In the article "Eagle fledglings, known nests down across county, state" from the New Jersey Herald, the focus was on Sussex County where the number of young eagles dropped from 20 in 10 known nests, to 12 in only 8 observed nests this past spring.

A nest on Minisink Island in the Delaware River had nesting eagles on February 28 but it was reported that the nest failed on March 9 after a major storm moved through the area the week before. That storm brought a temperature drop from the 60s to the low 40s, along with high winds, hail and more than a half-inch of rain.

Nest mortality often takes 4 of 5 fledglings before they reach maturity.

Sometimes our Jersey eagles leave the state. One female eagle that was banded in 2009 at the Newton Reservoir site has been spotted from Maryland to New York. Another Newton eagle banded in 2011 is now nesting at a reservoir near Middletown, N.Y.  Borders don't mean anything to eagles.

No comments:

Post a Comment