New Hampshire's peregrine falcon population continues to increase, with a record high 27 young raised this year in nests on natural cliffs, an urban building and an interstate highway bridge.

Because of the improvement in the status of peregrines, the Fish and Game Department recently moved the fast-flying raptor from the endangered to the threatened category on the state's List of Threatened and Endangered Wildlife.

However, there is concern that the birds are threatened by flame-retardant chemicals called PBDEs.

Overall, the peregrine breeding population in New Hampshire has increased by 50 percent over the past decade. The average number of young doubled in the last decade to 22.5.

This year, 27 young peregrines reached fledging age, equaling a record high set in 2002, said Chris Martin, who coordinates the state's peregrine monitoring program.

He and a team of rock-climbing volunteers reached nine peregrine nests this year, examining and banding 16 nestlings at seven productive sites and recovering nine eggs that went unhatched.

The bands examined showed a 13-year-old male raised in Dixville Notch and breeding in Franconia Notch, an 11-year-old male from Stark that has been confirmed breeding near Orford for 11 years. Two more New Hampshire-raised birds were found breeding on the Logan Airport control tower and at the University of Massachusetts in Amherst.

The unhatched eggs will be used to study the impact of contaminants on New England peregrines. Similar egg-collection efforts over past years are providing information about contaminants in wildlife.

For example, flame-retardant chemicals, called polybrominated diphenyl ethers or PBDEs, are commonly added to many consumer products. Martin said PBDEs gradually escape into the environment and contaminate air, water, soil, wildlife and humans.