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The cliffs of the Porcupine River are an important nesting habitat for peregrine falcons.
Their numbers dropped to very low levels during the 1960's and 1970's. In Alaska, peregrines of
the Porcupine River are monitored by annual surveys during mid July by biologists of the Arctic
Refuge. Since about 1980, the population of peregrines nesting on the Porcupine River have
steadily increased, and are now at levels several times greater than during the 1960's.
The decline of peregrine falcons on the Porcupine River was part of a continent-wide decline that
been linked to the use of the pesticide, DDT. As levels of the pesticide accumulated in the
peregrines, it caused thinning of their eggshells, which reduced productivity and caused
populations to decline. Because of the great reduction in peregrines, they were placed on the
endangered species list. Since the early 1970's, the use of DDT has been banned in both the U.S.
and Canada, and the eggshell thinning problem has diminished, allowing populations of
peregrines to increase as the Porcupine River data shows. In 1999, the American peregrine
falcon was officially removed from endangered species status in the United States.
Production of young peregrines is also sensitive to annual variation in weather conditions. For
example, colder than normal spring weather during 1989 and 1992 resulted in delayed migration
of birds to the Porcupine River (See graph of young produced). The primary food of peregrine
falcons are other birds, and if food is in short supply, peregrine breeding and production of young
Peregrine falcons are at the top of the food chain and thus are very sensitive indicators of
accumulation of contaminants like DDT in the environment. Because of the continuing
development of new chemicals, some of which might prove to be dangerous, it is important to
continue to monitor peregrine falcons as an indicator of environmental health.
The Porcupine River population of peregrines are of the subspecies: Falco peregrinus anatum or
the American peregrine falcon. In Alaska, annual surveys are conducted during mid July by
biologists of the Arctic Refuge.
Note: This is the MapCruzin.com archive of the FWS Arctic National Wildlife Refuge website. In December, 2001 FWS took this website offline, making it unavailable to the public. It includes 90 plus pages of information and many maps. As of 2006 the important information contained in this, the original "unsanitized" version of the FWS website, has yet to return to the internet, so we will continue to maintain it here as a permanent archive to help inform activists and concerned citizens. If you find any broken links, please report them to me at firstname.lastname@example.org and I will attempt to make the repairs. January, 2008 update - A small part of the original information that was present in 2001 has made it back into the current ANWR website. There is also an archive that contains a small amount of the original information, but it is not readily available from the main website.
U.S. Fish and Wildlife Service. 2001. Potential impacts of proposed oil and gas
development on the Arctic Refuge’s
coastal plain: Historical overview and
issues of concern. Web page of the Arctic National
17 January 2001. http://arctic.fws.gov/issues1.html
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