The number of Arctic peregrine falcons continued to increase and in 1991, the USFWS began reviewing the Arctic peregrine’s threatened status to determine if a proposal to delist was appropriate. By 1984, the recovery of Arctic peregrine falcons had progressed sufficiently that the USFWS reclassified the subspecies as threatened. This was particularly true in northern areas, where pesticide exposure was lower and impacts upon populations were less severe. Breeding surveys conducted in widely scattered areas showed that productivity rates returned to normal after the restrictions and as a result, populations expanded. These restrictions were the most pivotal action in aiding the recovery of the peregrine falcon and Arctic peregrine falcons recovered substantially after organochlorine pesticide use was curtailed. (their use had been restricted in Canada in 1970). įollowing the passage of the Endangered Species Act in 1973, the use of DDT and other organochlorines became severely restricted in the U.S. Populations are thought to have decreased by as much as 80%. Arctic peregrine numbers reached their lowest levels in the early 1970s and in some areas of North America successful reproduction virtually ceased. Probably the most serious problem resulted from DDE, the principal metabolite of DDT, which prevents normal calcium deposition during eggshell formation, causing eggs to frequently break before hatching. Heavily contaminated females may fail to lay eggs and organochlorines passed from the female to the egg can kill the embryo before it hatches. Organochlorine pesticides cause direct mortality and reduced reproduction in birds of prey who, being at the top of the food chain, ingest high doses of pesticides concentrated and stored in the fatty tissue of prey animals that themselves ingested contaminated food. Scientists investigating the peregrine's decline found unusually high concentrations of the pesticide DDT and its breakdown product DDE in peregrine falcons and other birds of prey. These declines were linked to organochlorine pesticides that were put into use following World War II, and whose use peaked in the late 1950s-early 1960s. Severe declines in peregrine falcon numbers began in the 1950s. It is a long-distance migrant that winters in Latin America from Cuba and Mexico south through Central and South America. The Arctic peregrine nests in tundra regions of Alaska, Canada (Yukon, Northwest Territories, Quebec, and possibly Labrador), and the ice-free perimeter of Greenland. The Arctic peregrine falcon (Falco peregrinus tundrius) is one of three subspecies of peregrine falcon.
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