There is a special something that happens in the soul when a human looks up to see an eagle soaring. Some American Indian cultures are built around eagles and the American founding fathers made the bald eagle the symbol of the country, despite the contrary opinion of Benjamin Franklin.

Now comes word that Sussex County’s bald eagle population doubled this year with confirmation a new pair has built, and appears to be using, a nest in Sparta. Last year, a pair raised two young in a nest on the shores of Little Swartswood Lake in Stillwater, the first confirmed nest in the county in several decades. That pair appears to be caring for eggs again this year, according to state officials.

Last year there were 55 active nests in New Jersey of which 47 nests produced 82 young.

“We believe there’s going to be four to five new active nests this year over last year,” said Kathleen Clark, principal biologist for the state Department of Environmental Protection’s endangered species program. “Over the last five years, we’ve seen new records, three to five new nests per year,” she said.

While the location of eagle nests is only publicized in general terms by state and federal officials, the specific location is usually an open secret in the areas where eagles are found. With a growing population of bald eagles, nests now are often located much closer to human habitation, despite the eagles’ well-known aversion to human disruption.

Last year, the pair on Little Swartswood Lake were quickly spotted by the public and DEP personnel set up buoys in the lake to keep boaters the recommended minimum 1,000 feet away from an active nest. This past winter, the presence of ice fishermen on the lake seemed to be upsetting the eagles, even though the anglers were outside the markers.

DEP expanded the prohibited territory, a move which the eagles apparently liked since they are tending a clutch of eggs.

One problem for the new nests may arrive as the weather warms up and human outdoor activity increases. “What may be deserted and looks great to a pair of eagles in December (when nest building begins), could be heavily used in May,” said Clark. The Sparta location fits that description.

The fear of more human activity around new nests is also a concern for Pat Lynch, chief biologist for the National Park Service in the Delaware Water Gap National Recreation Area, a 70,000-acre preserve which straddles the border between New Jersey and Pennsylvania.

Biologists there have spotted three active nests and one possible active nest, all on the Pennsylvania side of the river. One of the active nests is also readily accessible to the public.

Bald eagles take five years to mature and get their distinctive white heads and tails. At that point, they pair up and will stay mated until one of the set dies. Often an older eagle which has lost its mate will pair off with a young eagle and the newly paired couple will use the nesting site of the older partner.

It is possible, Lynch said, for a nest to have been used for several years and neither of the original nest builders is still alive. An eagle in the wild, once it matures, lives about 10 years, but there’s an estimated 80 percent mortality rate among juvenile eagles.

A pair can also outlive the life of a nest. One pair was on an active nest on the New Jersey side of the park in 2005 when a windstorm blew the nest out of the tree. Biologists recovered two eaglets, but one had a broken wing and could not be put back in the wild.

A temporary nest was built for the other youngster which the parents cared for until it learned to fly and left home.

While the 2005 adult pair finished raising that chick, the pair then disappeared. Because they were not banded, Lynch said it’s not known if that is the same pair which has established the new nest. This new site, in an oak tree in full view of the river, was partially built by the pair early last year.

It may take a couple of years for a pair of young eagles to “learn” to nest.

“They practice,” Lynch said. “They may build two or three nests. They may abandon a nest because it was being disturbed. When they decide on a spot, they begin housekeeping,” a sign they are laying eggs and trying to raise a brood.

The bald eagle population in the contiguous 48 states was down to a precious handful of successful nesting pairs in the 1960s and 1970s because of contamination from the pesticide DDT. While it did not kill eagles, DDT caused the eggs laid by females to have such thin shells, they would break in the nest.

In 1976, New Jersey had just one nesting pair, located in Bear Swamp in the southern part of the state. For six years, the pair tended to eggs, but no chicks hatched. Beginning in 1982, humans climbed into the nest, carefully removed the eggs and incubated them until they hatched.

The hatchlings were returned to the nest and the adult eagles successfully hacked ( raised ) several young.

The state began its own hacking program in the 1980s, importing very young eaglets from Manitoba which were then raised. Because they were brought here at a young age, the eagles imprinted on this area as their home territory.

The theory is that eagles, as they mature, will wander back to their home territory to find a mate and raise their own young. For the most part, the theory has proven correct and only Vermont still has a “hacking” program.

Eagles have rebounded so well there are hearings schedule this year on a move to take the bald eagle off the federal endangered species list, although several other federal and most state laws will still provide protection.

The state effort is augmented by a strong volunteer corps which provides much of the observation and protection of the eagle sites. “It takes a good neighborhood to protect an eagle nest,” Clark said. “They are our eyes and ears out there.”

The general public can also help. There is a check-off line on the state income tax form with the money going to the endangered species program. Fees from special license plates also go to the fund.

As the population of eagles grows, nesting pairs will begin filling in habitat that is suitable and settle territorial disputes among themselves. As to tolerance of humans, Clark said individual birds may adapt, “but I don’t see tolerance changing as a species.”

And that will create more challenges in keeping a necessary separation.

“For people, it’s natural to want a close wildlife experience,” said Clark. “And eagles are always going to be high on that special scale.”