taichiliberal
Rookie
- Aug 11, 2010
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- #81
DDT was linked to causing sub par eggs in bald eagles. Do the research, because I'm damned tired of doing it for willfully ignorant parrots like you. If you won't, then I'll embarass you further with the documented facts.
Egg shell thinning is not correlated with pesticide residues. [Krantz WC. 1970 (No correlation between shell-thinning and pesticide residues in eggs) Pesticide Monitoring J 4(3): 136-141; Postupalsky, S. 1971. Canadian Wildlife Service manuscript, April 8, 1971 (No correlation between shell-thinning and DDE in eggs of bald eagles and cormorants); Anon. 1970. Oregon State University Health Sciences Conference, Annual report, p. 94. (Lowest DDT residues associated with thinnest shells in Cooper's hawk, sharp-shinned hawk and goshawk); Claus G and K Bolander. 1977. Ecological Sanity, David McKay Co., N.Y., p. 461. (Feeding thyreprotein causes hens to lay lighter eggs, with heavier, thicker shells)
After 15 years of heavy and widespread usage of DDT, Audubon Society ornithologists counted 25 percent more eagles per observer in 1960 than during the pre-DDT 1941 bird census. [Marvin, PH. 1964 Birds on the rise. Bull Entomol Soc Amer 10(3):184-186; Wurster, CF. 1969 Congressional Record S4599, May 5, 1969; Anon. 1942. The 42nd Annual Christmas Bird Census. Audubon Magazine 44:1-75 (Jan/Feb 1942; Cruickshank, AD (Editor). 1961. The 61st Annual Christmas Bird Census. Audubon Field Notes 15(2):84-300; White-Stevens, R.. 1972. Statistical analyses of Audubon Christmas Bird censuses. Letter to New York Times, August 15, 1972]
U.S. Fish and Wildlife Service biologists fed large doses of DDT to captive bald eagles for 112 days and concluded that DDT residues encountered by eagles in the environment would not adversely affect eagles or their eggs. [Stickel, L. 1966. Bald eagle-pesticide relationships. Trans 31st N Amer Wildlife Conference, pp.190-200]
Every bald eagle found dead in the U.S., between 1961-1977 (266 birds) was analyzed by U.S. Fish and Wildlife Service biologists who reported no adverse effects caused by DDT or its residues. [Reichel, WL. 1969. (Pesticide residues in 45 bald eagles found dead in the U.S. 1964-1965). Pesticides Monitoring J 3(3)142-144; Belisle, AA. 1972. (Pesticide residues and PCBs and mercury, in bald eagles found dead in the U.S. 1969-1970). Pesticides Monitoring J 6(3): 133-138; Cromartie, E. 1974. (Organochlorine pesticides and PCBs in 37 bald eagles found dead in the U.S. 1971-1972). Pesticides Monitoring J 9:11-14; Coon, NC. 1970. (Causes of bald eagle mortality in the US 1960-1065). Journal of Wildlife Diseases 6:72-76]
Many experiments on caged-birds demonstrate that DDT and its metabolites (DDD and DDE) do not cause serious egg shell thinning, even at levels many hundreds of times greater than wild birds would ever accumulate. [Cecil, HC et al. 1971. Poultry Science 50: 656-659 (No effects of DDT or DDE, if adequate calcium is in diet); Chang, ES & ELR Stokstad. 1975. Poultry Science 54: 3-10 1975. (No effects of DDT on shells); Edwards, JG. 1971. Chem Eng News p. 6 & 59 (August 16, 1971) (Summary of egg shell- thinning and refutations presented revealing all data); Hazeltine, WE. 1974. Statement and affidavit, EPA Hearings on Tussock Moth Control, Portland Oregon, p. 9 (January 14, 1974); Jeffries, DJ. 1969. J Wildlife Management 32: 441-456 (Shells 7 percent thicker after two years on DDT diet); Robson, WA et al. 1976. Poultry Science 55:2222- 2227; Scott, ML et al. 1975. Poultry Science 54: 350-368 (Egg production, hatchability and shell quality depend on calcium, and are not effected by DDT and its metabolites); Spears, G & P. Waibel. 1972. Minn. Science 28(3):4-5; Tucker, RK & HA Haegele. 1970. Bull Environ Contam. Toxicol 5:191-194 (Neither egg weight nor shell thickness affected by 300 parts per million DDT in daily diet);Edwards, JG. 1973. Statement and affidavit, U.S. Senate Committee on Agriculture, 24 pages, October 24, 1973; Poult Sci 1979 Nov;58(6):1432-49 ("There was no correlation between concentrations of pesticides and egg shell thinning.")]
Experiments associating DDT with egg shell thinning involve doses much higher than would ever be encountered in the wild. [J Toxicol Environ Health 1977 Nov;3(4):699-704 (50 ppm for 6 months); Arch Environ Contam Toxicol 1978;7(3):359-67 ("acute" doses); Acta Pharmacol Toxicol (Copenh) 1982 Feb;50(2):121-9 (40 mg/kg/day for 45 days); Fed Proc 1977 May;36(6):1888-93 ("In well-controlled experiments using white leghorn chickens and Japanese quail, dietary PCBs, DDT and related compounds produced no detrimental effects on eggshell quality. ... no detrimental effects on eggshell quality, egg production or hatchability were found with ... DDT up to 100 ppm)]
Laboratory egg shell thinning required massive doses of DDE far in excess of anything expected in nature, and massive laboratory doses produce much less thinning than is seen in many of the thin-shelled eggs collected in the wild. [Hazeltine, WE. 1974. Statement and affidavit, EPA Hearings on Tussock Moth Control, Portland Oregon, p. 9 (January 14, 1974)]
Years of carefully controlled feeding experiments involving levels of DDT as high as present in most wild birds resulted in no tremors, mortality, thinning of egg shells nor reproductive interference. [Scott, ML et al. 1975. Poultry Science 54: 350-368 (Egg production, hatch ability and shell quality depend on calcium, and are not effected by DDT and its metabolites)]
Egg shell thinning is not correlated with pesticide residues. [Krantz WC. 1970 (No correlation between shell-thinning and pesticide residues in eggs) Pesticide Monitoring J 4(3): 136-141; Postupalsky, S. 1971. Canadian Wildlife Service manuscript, April 8, 1971 (No correlation between shell-thinning and DDE in eggs of bald eagles and cormorants); Anon. 1970. Oregon State University Health Sciences Conference, Annual report, p. 94. (Lowest DDT residues associated with thinnest shells in Cooper's hawk, sharp-shinned hawk and goshawk); Claus G and K Bolander. 1977. Ecological Sanity, David McKay Co., N.Y., p. 461. (Feeding thyreprotein causes hens to lay lighter eggs, with heavier, thicker shells)
DDT was blamed for egg shell thinning even though a known egg shell thinner (dieldrin) was also added to the diet. [Porter, RD and SN Wiemeyer. 1969. Science 165: 199-200]
No significant correlation between DDE and egg shell thinning in Canadian terns even though the eggs contained as much as 100 parts per million of DDE. [Switzer, BG et al. 1971. Can J Zool 49:69-73]
Birds played a major role in creating awareness of pollution problems. Indeed, many people consider the modern environmental movement to have started with the publication in 1962 of Rachel Carson's classic Silent Spring, which described the results of the misuse of DDT and other pesticides. In the fable that began that volume, she wrote: "It was a spring without voices. On the mornings that had once throbbed with the dawn chorus of robins, catbirds, doves, jays, wrens, and scores of other bird voices there was now no sound; only silence lay over the fields and woods and marsh." Silent Spring was heavily attacked by the pesticide industry and by narrowly trained entomologists, but its scientific foundation has stood the test of time. Misuse of pesticides is now widely recognized to threaten not only bird communities but human communities as well.
The potentially lethal impact of DDT on birds was first noted in the late 1950s when spraying to control the beetles that carry Dutch elm disease led to a slaughter of robins in Michigan and elsewhere. Researchers discovered that earthworms were accumulating the persistent pesticide and that the robins eating them were being poisoned. Other birds fell victim, too. Gradually, thanks in no small part to Carson's book, gigantic "broadcast spray" programs were brought under control.
But DDT, its breakdown products, and the other chlorinated hydrocarbon pesticides (and nonpesticide chlorinated hydrocarbons such as PCBs) posed a more insidious threat to birds. Because these poisons are persistent they tend to concentrate as they move through the feeding sequences in communities that ecologists call "food chains." For example, in most marine communities, the living weight (biomass) of fish-eating birds is less than that of the fishes they eat. However, because chlorinated hydrocarbons accumulate in fatty tissues, when a ton of contaminated fishes is turned into 200 pounds of seabirds, most of the DDT from the numerous fishes ends up in a relatively few birds. As a result, the birds have a higher level of contamination per pound than the fishes. If Peregrine Falcons feed on the seabirds, the concentration becomes higher still. With several concentrating steps in the food chain below the level of fishes (for instance, tiny aquatic plants crustacea small fishes), very slight environmental contamination can be turned into a heavy pesticide load in birds at the top of the food chain. In one Long Island estuary, concentrations of less than a tenth of a part per million (PPM) of DDT in aquatic plants and plankton resulted in concentrations of 3-25 PPM in gulls, terns, cormorants, mergansers, herons, and ospreys.
"Bioconcentration" of pesticides in birds high on food chains occurs not only because there is usually reduced biomass at each step in those chains, but also because predatory birds tend to live a long time. They may take in only a little DDT per day, but they keep most of what they get, and they live many days.
The insidious aspect of this phenomenon is that large concentrations of chlorinated hydrocarbons do not usually kill the bird outright. Rather, DDT and its relatives alter the bird's calcium metabolism in a way that results in thin eggshells. Instead of eggs, heavily DDT-infested Brown Pelicans and Bald Eagles tend to find omelets in their nests, since the eggshells are unable to support the weight of the incubating bird.
Shell-thinning resulted in the decimation of the Brown Pelican populations in much of North America and the extermination the Peregrine Falcon in the eastern United States and southeastern Canada. Shell-thinning caused lesser declines in populations of Golden and Bald Eagles and White Pelicans, among others. Similar declines took place in the British Isles. Fortunately, the cause of the breeding failures was identified in time, and the use of DDT was banned almost totally in the United States in 1972.
The reduced bird populations started to recover quickly thereafter, with species as different as ospreys and robins returning to the pre-DDT levels of breeding success in a decade or less. Furthermore, attempts to reestablish the peregrine in the eastern United States using captive-reared birds show considerable signs of success. Brown Pelican populations have now recovered to the extent that the species no longer warrants endangered status except in California. The banning of DDT has helped to create other pesticide problems, however. The newer organophosphate pesticides that to a degree have replaced organochlorines, such as parathion and TEPP (tetraethyl pyrophosphate), are less persistent so they do not accumulate in food chains. They are, nonetheless, highly toxic. Parathion applied to winter wheat, for instance, killed some 1,600 waterfowl, mostly Canada Geese, in the Texas panhandle in 1981.
Unfortunately, however, DDT has recently started to become more common in the environment again; its concentration in the tissues of starlings in Arizona and New Mexico, for example, has been increasing. While the source of that DDT is disputed, what is certain is that DDT has been shown to be present as a contaminant in the widely used toxin dicofol (a key ingredient in, among others, the pesticide Kelthane). Dicofol is a chemical formed by adding single oxygen atoms to DDT molecules. Unhappily, not all the DDT gets oxygenated, so that sometimes dicofol is contaminated with as much as 15 percent DDT
Overall, the 2.5 million pounds of dicofol used annually in pesticides contain about 250 thousand pounds of DDT. In addition, little is known about the breakdown products of dicofol itself, which may include DDE, a breakdown product of DDT identified as the major cause of reproductive failure in several bird species. Finally, DDT itself may still be in use illegally in some areas of the United States, and migratory birds such as the Black-crowned Night-Heron may be picking up DDT in their tropical wintering grounds (where DDT application is still permitted). Unhappily tropical countries are becoming dumping grounds for unsafe pesticides that are now banned in the United States. As the end of the century approaches, the once hopeful trend may be reversing, so that DDT and other pesticides continue to hang as a heavy shadow over many bird populations.
DDT and Birds