Peregrine falcon numbers continue to rise in New Jersey, but the species is still recovering from the effects of dangerous chemicals released into the environment decades ago.
That's the conclusion drawn by the 2009 peregrine falcon report, which was released earlier this month by the state Department of Environmental Protection's Division of Fish and Wildlife.
New Jersey has 24 documented nesting pairs of peregrine falcons this year, up from 20 nesting pairs that were identified in the 2008 report.
The number of nesting pairs increased after four pairs were discovered along bridges that connect New Jersey to Pennsylvania.
Many of the existing pairs can be found along New Jersey's coastal areas. This year, those nests were considered very successful, with 11 of 14 pairs producing 27 new peregrine falcon chicks during the course of the year.
With new discoveries made each year, it is possible that even more peregrine falcons could be found throughout the state.
"They can be really hard to pin down," said Kathleen Clark, a biologist with the Division of Fish and Wildlife's endangered species program who helped put together this year's report.
Many peregrine nests in New Jersey are found on manmade structures such as bridges and the Atlantic City Hilton Casino Resort, where three peregrine chicks hatched in 2009.
Because of these nest-building trends, pairs can be difficult to track. Clark said the birds often build nests in places that are difficult to monitor and in many cases cannot even be seen. That's why even though a peregrine may be spotted, biologists cannot confirm whether it is from New Jersey until they have found a nest.
"I know there are peregrines still in Newark," Clark said. "But I can't find them."
The difficulty in tracking down nesting pairs extends into southern New Jersey as well. A nest for a pair of peregrines may be located underneath a portion of bridge that runs along Great Bay Boulevard in Little Egg Harbor Township's Mystic Islands, but biologists will not list the peregrines as a nesting pair unless they see it with their own eyes.
"We haven't gotten underneath that bridge to get a look at that pair," said Ben Wurst, habitat program manager for Conserve Wildlife New Jersey.
Peregrine populations have rebounded significantly since every nesting pair east of the Mississippi River was wiped out due to the overuse of the pesticide DDT in the 1960s. The chemical caused eggshells to thin and lowered the survival rate for peregrine chicks.
While DDT is no longer used as a pesticide in the United States, evidence of its past use can still be seen to this day. Clark said peregrine egg shells, especially along New Jersey's coastline, are still thinner than they should be.
A new threat facing many peregrines is a parasitic fly. Many nests that were inspected were home to several wingless flies that latched onto the birds.
"They suck the blood of little nestlings," Wurst said. "They're killing peregrine chicks when they're very young." 
Wurst said these pests can be eliminated with an alcohol spray, and the birds are not put at risk from the use of the spray.
To view the entire 2009 Peregrine Falcon report, visit:
http://www.state.nj.us/dep/fgw/ensp/pdf/pefa09_report.pdfA peregrine falcon soars during the annual Hawk Watch at Cape May Point State Park.
