Ddt and Its Affects on Peregrine Falcons

The Peregrine Falcon (Falco peregrinus), or Duck Hawk, is a medium-sized raptor weighing 2 to 2 pounds. These remarkable birds of prey measure 15-21 inches and have a wingspan of about 3  feet. Their name, Peregrine, comes from the Latin word peregrinus, which means “to wander”. The name fits, given that they have one of the longest migrations in North America and are found on every continent besides Antarctica. Peregrine Falcon’s hunt pigeons, crows, waterfowl, starlings, jays, and other small to medium-sized birds. They are also known to hunt for bats and other small mammals (Defenders of Wildlife).

They are best known for their spectacular hunting methods in which they catch their prey mid-air. If that is not impressive enough, they do it while plunging at speeds of up to 200 miles per hour, killing or stunning their prey instantly (National Geographic). What is even more impressive than any of this is the fact that the Peregrine Falcon was on the verge of extinction and has made a remarkable comeback. The cause of their brush with extinction was the result of the use of organochlorine pesticides, mainly dichloro-diphenyl trichloroethane (DDT) (The Santa Cruz Predatory Bird Research Group).

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DDT was first synthesized in 1874. However, its effectiveness as an insecticide was not discovered until 1939. This discovery was made by Dr. Paul Herman Muller of Switzerland. Muller worked as a laboratory technologist at the great dye-manufacturing firm of J. R. Geigy. Muller started working on inventing new insecticides in 1936 and by 1939 had synthesized DDT. After years of perfecting the new compound, he proved its effectiveness in controlling Colorado Potato Beetles on crops. During WWII, he also found it just as effective in destroying lice on war refugees.

As testing continued, Muller and his associates were convinced that he had discovered the most potent insecticide known at the time. DDT was fatal to insects in a very minute quantity, yet was completely non-toxic to humans. Geigy, the company that Muller worked for, patented the formula in 1940 and the manufacture of DDT began. The need for an insecticide during the war was one of absolute necessity. At the time, the main source of insecticides was a flower imported by Japan. War with Japan cut off the major source, and with no effective and safe insecticides, the U.S. became desperate.

With the spread of malaria carried by mosquitoes, and the fact that Japan had cut off exports, DDT gained attention. The popularity of DDT grew when in 1943 the U. S. Army placed it on supply lists. By the end of the war, DDT had become the most publicized synthetic chemical in the world. After 1945, DDT became widespread in the U. S. for commercial and agricultural use. The popularity was due to its effectiveness, cost, versatility, and persistence. Dr. Paul Herman Muller was awarded a Nobel Prize for his discovery of this remarkable insecticide in 1948 (Davis).

The next 30 years would be a wake-up call to many people around the globe. The long-term effects of DDT were still a mystery, but would soon surface. During the same time that Dr. Paul Herman Muller was perfecting the DDT compound in Switzerland, a woman named Rachel Carson was teaching in the zoology department of the University of Maryland. During her college years, she had majored in English composition and biology. Her desire to write landed her a job with the U. S. Bureau of Fisheries before it became the Fish and Wildlife Service. Her career prospered in the following years.

In 1941 she wrote her first book, Under the Sea Wind, which had won critical acclaim and earned her the position of Editor In Chief of the Fish and Wildlife Service. With this new position, she was required to read a large deal about the new insecticide, DDT. She was not happy with what she read about experiments that had been going on. One experiment told of a gypsy-moth-infested 1,200-acre oak forest that was sprayed in Pennsylvania. Every gypsy-moth caterpillar had died within a few hours. Along with the target species, every bird and ladybug also died. About 4,000 birds died in eight days.

Moreover, as a cause of the ladybugs being extirpated, came a tremendous multiplication of aphids. The aphids were not affected by the DDT, and with no ladybugs to control their population, the forest was on the verge of being defoliated. The water-vulnerable aphids were held under control when rains stopped the outbreak. Reading about these experiments encouraged Carson to become an advocate for the prevention of DDT use (Davis). In 1951, Rachel Carson became famous when she wrote The Sea Around Us. It sold so well that she became financially independent.

In the next few years, she wrote another book and gained more fame. Then in 1958, a good friend of Carson’s wrote a letter to her explaining the effects that DDT has had on their private 2-acre bird sanctuary at Powder Point. Soon thereafter, Carson stayed as a guest at Powder Point and late one afternoon the DDT spraying plane came over. The next morning Carson went through the estuary in a boat and was disturbed by what she saw. Dead and dying fish were everywhere. There were crayfish and crabs that were dead or staggering as their nervous systems were destroyed.

Her friend convinced her that she must write about the effects that DDT is having. During the next 4 years, she wrote Silent Spring (Davis). It was the publication of this book in 1962 that stimulated widespread public concern over the use of DDT. Carson’s book told of the dangers of improper pesticide use and the need for better pesticides. It was now obvious that DDT should undergo some intense investigation. Over the next ten years, DDT use was slowly but dramatically reduced. DDT spraying was reduced from 4.9 million acres in 1957 to just over 100,000 acres in 1967.

After years of trials and experiments, it was banned for nearly all purposes in 1972 (Environmental Protection Agency). The effects of DDT on Peregrine Falcons were significant due to bioaccumulation. As DDT spread through the food chain, it reached endocrine hormone-disrupting levels by the time it was spread to top predators, such as the Peregrine Falcon. One of the main products of DDT, dichloro-diphenyl-ethylene (DDE), caused catastrophic results to the reproduction of many carnivorous birds.

DDE caused abnormal reproductive behavior by the parent birds, hatching failure, addling, and most commonly, eggshell thinning. As DDE accumulated in the fatty tissue of these birds, the stored chemical acted to ‘block’ the movement of calcium during eggshell formation. This lack of sufficient calcium in the eggshells caused them to be susceptible to breakage during incubation. Eggshell thinning and nesting failures were widespread in North America during the period of DDT use (The Santa Cruz Predatory Bird Research Group). In some regions, successful reproduction virtually stopped.

Peregrine Falcons nesting east of the Mississippi River, where DDT was most heavily used, were extirpated by the mid-1960s. No active Peregrine Falcon nests were found in surveys of 133 previously used nests in the latter part of the 1964 nesting season in eastern North America. They were also extirpated in the Great Plains region. By 1975, there were only three pairs of Peregrine Falcons in Alberta, and no other pairs were found south of latitude 60° N, and east of the Rocky Mountains. West of the 100th meridian, only 33 percent of historical nesting sites were still occupied by 1965.

Peregrine Falcons were listed as endangered in 1970 under the Endangered Species Conservation Act of 1969 (Fish and Wildlife Service). It is estimated that before the 1940s there were around 3,875 nesting pairs in North America. However, by 1975 there were only 324 known nesting pairs in the United States (Center for Biological Diversity). Since 1975, the Peregrine Falcon has made a strong comeback. Captive breeding programs were set up to boost the bird’s numbers in the United States and Canada. Populations are now strong in those nations.

In some parts of the world, there may even be more Peregrine Falcons than there were before the decline. Programs or groups were set up during the late 1970s and 1980s in different regions. Among these regions, the Eastern regions have seen the most improvement in Peregrine Falcon populations. This is a major accomplishment being that they were completely extirpated during the 1960s. Most of these programs involved ‘hacking’ the birds back into their environment. This involved raising chicks to a mature age, then releasing them into the wild without guardians.

Thanks to programs that support the Peregrine Falcon, they made a strong comeback. In 1998, the total known number of breeding pairs was 1,650 pairs in the United States and Canada, far surpassing the 456 required for delisting. Peregrine Falcons were delisted from the Endangered Species list in 1999 (Center for Biological Diversity). The future for the Peregrine Falcon looks promising. Monitoring of their populations has continued as part of a post-delisting monitoring plan. Beginning in 2003, data will be collected every three years and presented in triennial reports.

These reports will continue until 2015, and as of right now, it looks as is if the Peregrine Falcon will meet and exceed their expectations (Center for Biological Diversity). The last 60 years have been a test for the Peregrine Falcon. As DDT use rose, the Peregrine Falcon population plummeted to near extinction. Through awareness and active groups, this spectacular bird has stood the test and has now soared back to outstanding numbers.

Terrestrial Pairs Nesting Pairs Young Fledged
1982-1986 4 1 0
1987 6 3 1
1988 13 8 12
1989 16 12 22
1990 23 16 33
1991 30 22 36
1992 37 32 68
1993 53 43 87
1994 62 51 116
1995 67 53 118

 Data provided – (Tordoff and Redig)

Works Cited

  1. Center for Biological Diversity. 2009. 2 November 2009 <http://www. biologicaldiversity.org/campaigns/esa_works/profile_pages/AmericanPerigrineFalcon. html>.
  2. Davis, Kenneth S. American Heritage. February 1971. 28 October 2009 <http://www. americanheritage.com/articles/magazine/ah/1971/2/1971_2_44. shtml>.
  3. Defenders of Wildlife. 2009. 28 October 2009 <http://www. defenders.org/wildlife_and_habitat/wildlife/peregrine_falcon. php>.
  4. Environmental Protection Agency. July 1975. October 2009 <http://www. epa. gov/history/topics/ddt/02. htm>.
  5. Fish and Wildlife Service. 25 August 1999. 28 October 2009 <http://frwebgate. access. gpo. gov/cgi-bin/getdoc. cgi? dbname=1999_register&docid=99-21959-filed>.
  6. National Geographic. 2009. 28 October 2009 <http://animals. nationalgeographic.com/animals/birds/peregrine-falcon. html>.
  7. The Santa Cruz Predatory Bird Research Group. 2007. 28 October 2009 <http://www2. ucsc. edu/scpbrg/ddt. htm>.
  8. Tordoff, Harrison B. and Patrick T. Redig. “Midwest Peregrine Falcon Demography 1982-1995. ” December 1997. The Raptor Research Foundation. 2 November 2009

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Ddt and Its Affects on Peregrine Falcons. (2016, Aug 22). Retrieved from https://graduateway.com/ddt-and-its-affects-on-peregrine-falcons/