The beginning of Pacific Coast Peregrine Watch
Since 1969, Bob Isenberg has been observing peregrines along the Central Coast of California. As of January 2012, he has spent over 17,700 hours. In the past four years, five to six hours were spent in observation daily. Previously, time was spent on late afternoons and weekends.
During the 1950s, 60s and 70s, DDT and related organochlorine pesticides went up the food chain ending up in the fat of the falcons. When eggs were laid, the shells became too thin to survive incubation due to the lower amount of calcium found in the eggshells. The populations of these raptors plummeted in the 1960s. DDT has been banned in the United States since the 1970s and peregrine populations have recovered with the help of protection of nesting places and peregrines released into the wild. They are now found nesting in urban areas on skyscrapers, window ledges and have found pigeons and other urban birds to be good food sources.