It’s probably fair to say that, were she alive today, scientist and author Rachel Carson would be thrilled to find that a pair of peregrine falcons has again elected to build a nest on a ledge of the state office building in Harrisburg, PA that bears her name. Fledging young peregrines from the Rachel Carson State Office Building is especially fitting given Carson’s role in raising awareness of the terrible impacts of DDT on species such as peregrine falcons through her 1962 book, “Silent Spring.”

Peregrines were listed as an endangered species by the U.S. Fish and Wildlife Service in 1972 following the catastrophic decline of the species worldwide. Disturbance of cliff nesting sites, shooting and egg collecting have reduced populations, but the largest threat has been pesticides such as DDT.

DDT, an organochlorine compound used as a crop pesticide, was banned throughout North America in the 1970s. Organochlorines are toxic and persist in living tissues, resisting breakdown and resulting in bioaccumulation, particularly in long-lived predator species such as the peregrine. These pesticide residues result in female peregrines laying very thin-shelled eggs, which cannot sustain the weight of incubation.

The peregrine has since experienced one of the most dramatic recoveries of any endangered species, and was formally removed from the federal list in 1999. It continues to be listed by the Pennsylvania Game Commission as an endangered species because of the small local population and continued threats. There are now 32 nesting pairs of peregrine falcons across the state.

Now people around the globe can observe the activities of the Harrisburg pair by accessing the live Falcon-Cam hosted by the Pennsylvania Department of Environmental Protection.

Falcons have nested at the building for 12 years, producing 53 eggs and 45 hatchlings. Of these, 29 falcons survived; 13 males and 16 females. Last year, only one of four eggs successfully hatched. The first eggs of the 2012 breeding season will be laid in late March and begin to hatch around mid-May. The young falcons, or “eyases,” will take their first flights, or “fledge,” in mid-June.

Visit www.dep.state.pa.us/dep/falcon/default.htm to view the live falcons. Fans can also sign up for the Falcon Wire electronic newsletter or follow the falcons on Twitter at www.twitter.com/FalconChatter. See additional webcams on barn owls and great horned owls at watch.birds.cornell.edu/nestcams/home/index.