#
VI. Egg-shell thinning
DDT was alleged to have thinned bird egg shells.
#
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)]
#
Among brown pelican egg shells examined there was no correlation between DDT residue and shell thickness.
[Switzer, B. 1972. Consolidated EPA hearings, Transcript pp. 8212-8336; and Hazeltine, WE. 1972. Why pelican eggshells are thin. Nature 239: 410-412]
#
Egg shells of red-tailed hawks were reported to be six percent thicker during years of heavy DDT usage than just before DDT use began. Golden eagle egg shells were 5 percent thicker than those produced before DDT use.
[Hickey, JJ and DW Anderson. 1968. Science 162: 271-273]
To the extent egg shell thinning occurred, many other substances and conditions could have been responsible.
#
Oil has been associated with egg shell thinning.
[Anon. National Wildlife Federation, Conservation News, pp. 6-10, October 15 1979. (Embryonic mortality from oil on feathers of adults birds) ; Hartung, R. 1965. J Wildlife Management 29:872-874 (Oil on eggs reduces hatch ability by 68 percent); Libby, EE. 1978. Fish, wildlife and oil. Ecolibrium 2(4):7-10; King, KA et al. 1979 Bull Environ Contam Tox 23:800-805 (Oil a probably cause of pelican mortality for six weeks after spill);Albers, PH. 1977. Fate and Effects of Petroleum Hydrocarbons in Marine Ecosystems, Pergamon Press, N.Y. (Chapters 15 & 16; Dieter, MP. 1977. Interagency Energy-Environment Research and Development Program Report, pp. 35-42 (5 microliters of oil on fertile egg kills 76 to 98 percent of embryos within; birds ingesting oil produce 70 percent to 100 percent less eggs than normal; offspring failed to develop normal flight feathers); Szaro, RC. 1977. Proc 42nd N Amer Wildlife Nat Resources Conference, pp. 375-376]
#
Lead has been associated with egg shell thinning.
[Bellrose, RC. 1959. Ill Nat Hist Survey Bull 27:235-288 (Lead poisoning in wildlife)]
#
Mercury has been associated with egg shell thinning.
[D'Itri, FM & PB Trost. 1970. International Conference on Mercury Contamination, Ann Arbor, September 30, 1070; Scott, JL et al. 1975. Effects of PCBs, DDT and mercury upon egg production, hatch ability and shell quality. Poultry Sci 54:3350-368; Stoewssand, GS et al.. 1971. Shell- thinning in quail fed mercuric chloride. Science 173:1030-1031; Tucker, RK. 1971. Utah Science June 1971:47-49 (Effects of many chemicals on shell thickness).; Tucker, RK & HA Haegle. 1970. Bull Environ Contamin Toxicol 5:191-194]
#
Stress from noise, fear or excitement and disease are associated with egg shell thinning.
[Scott, HM et al.. 1944. (Physiological stress thins shells) Poultry Science 23:446-453; Draper, MH & PE Lake. 1967. Effects of stress and defensive responses. In Environmental Control in Poultry Production, Oliver and Boyd, London; Reid, BL. 1971. (Effects of stress on laying birds) Farm Technology, Fall 1971; Sykes, AH. 1955 (Adrenaline excess inhibits shell formation) Poultry Science 34: 622-628]
#
Older birds produce thinner shells.
[Sunde, ML. 1971 (Older birds produce thinner shells) Farm Technology, Fall 1971]
#
Normal egg shells become 5 percent thinner as developing embryos withdraw calcium for bone development.
[Romanoff, AL and AJ Romanoff. 1967. Biochemistry of the Avian Embryo, Wiley & Sons, N.Y.; Simkiss, K. 1967. (Shells thinned by embryo development within) In Calcium in Reproductive Physiology, Reinhold, NY, pp 198-213]
#
Larger birds tend to produce thicker-shelled eggs.
[Asmundson, VS et al. 1943. (Relations between the parts of birds' eggs) Auk 60:34-44]
#
Dehydration is associated with thinner egg shells.
[Tucker, RK and HA Haegle. 1970. (30 percent thinner shells formed after quail were kept from water for 36 hours) Bull Environ Contam Toxicol 5(3): 191-194]
#
Temperature extremes are associated with thinner egg shells.
[Romanoff, AL and AJ Romanoff, 1949. The Avian Egg, Wiley & Sons]
#
Decreased illumination is associated with thinner egg shells.
[Peakall, DB. 1970. (Shells not thinned even after illumination was abruptly reduced from 16 hours daily to 8 hours daily and high DDT dosage begun simultaneously) Science 168:592-594; Day, EJ. 1971. (Importance of even illumination on laying birds) Farm Technology, Fall 1971;Houser, EJ. 1962. Pacific Poultryman, August 1962; Morris, TR et al. 1964. (The most critical area of light duration is that between 16 hours and 8 hours daily) British Poultry Science 5: 133-147; Ward, P. 1972 (Physiological importance of photo period in bird experiments) Ibis 114: 275]
#
Human and predator intrusion is associated with thinner egg shells.
[Beatty, RG. 1973. The DDT Myth, John Day Co., N.Y. 201 pages; Anon. 1971. Hawk Chalk 10(3):47-57; Cade, TJ. 1960. Ecology of the peregrine and gyrfalcon populations in Alaska. Univ Calif Publ Zool 63(3): 151-290]
#
Simple restraint interferes with the transport of calcium throughout the body of birds, preventing adequate calcium from reaching the shell gland and forming good shells.
[Sykes, AH. 1955. Poultry Science 34:622-628]
#
Uncovering eggs after parent birds are removed or frightened off exposes eggs to potentially fatal chilling, especially in northern or high altitude locations.
[Cade, TJ. 1960. Ecology of the peregrine and gyrfalcon populations in Alaska. Uni Calif Publ Zool 63(3):151-290]
#
Phosphorus deficiency is associated with thinner shells.
[Crowley, TA et al. 1963. Poultry Science 54: 350-368]
#
Calcium deficiency is associated with thinner shells.
[Greely, F.. 196 (Effects of calcium deficiency) J Wildlife Management 70:149-153; Romanoff, AL and AJ Romanoff. 1949. The Avian Egg, Wiley & Sons; Scott, ML. 1975. Poultry Science 54:350-368; Taylor, TG. 1970. How and eggshell is formed. Scientific American 222:89-95; Tucker, RK and HA Tucker. 1970. Bull Environ Contamin Toxicol 5(3):1191-194]
#
Egg shell deficiencies were attributed to DDT and DDE by U.S. Fish and Wildlife researchers even though the birds had been placed on low-calcium diets.
[Bitman, J et al. 1969. Nature 224: 44-46; Bitman, J et al. 1970. Science 594-595. ]
#
Cutting illumination from 16 hours daily to 8 hours daily at the same time as DDT feeding began had no significant adverse effect on shell quality. Shell quality was only adversely impacted after large amounts of DDE were injected into birds.
[Peakall, DB. 1970. Science 168:592-594]
#
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]
VII. Bald eagles
DDT was blamed for the decline in the bald eagle population.
#
Bald eagles were reportedly threatened with extinction in 1921 -- 25 years before widespread use of DDT.
[Van Name, WG. 1921. Ecology 2:76]
#
Alaska paid over $100,000 in bounties for 115,000 bald eagles between 1917 and 1942.
[Anon. Science News Letter, July 3, 1943]
#
The bald eagle had vanished from New England by 1937.
[Bent, AC. 1937. Raptorial Birds of America. US National Museum Bull 167:321-349]
#
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]
#
No significant correlation between DDE residues and shell thickness was reported in a large series of bald eagle eggs.
[Postupalsky, S. 1971. (DDE residues and shell thickness). Canadian Wildlife Service manuscript, April 8, 1971]
#
Thickness of eggshells from Florida, Maine and Wisconsin was found to not be correlated with DDT residues.
Data from Krantz, WC. 1970. Pesticides Monitoring Journal 4(3):136-140.
State Thickness (mm) DDE residue (ppm)
Florida 0.50 About 10
Maine 0.53 About 22
Wisconsin 0.55 About 4
#
U.S. Forest Service studies reported an increase in nesting bald eagle productivity (51 in 1964 to 107 in 1970).
[U.S. Forest Service (Milwaukee, WI). 1970. Annual Report on Bald Eagle Status]
#
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]
#
Wildlife authorities attributed bald eagle population reductions to a "widespread loss of suitable habitat", but noted that "illegal shooting continues to be the leading cause of direct mortality in both adult and immature bald eagles."
[Anon.. 1978. U.S. Fish and Wildlife Service, Endangered Species Tech Bull 3:8-9]
#
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 dad 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]
#
U.S. Fish and Wildlife Service biologists linked high intake of mercury from contaminated fish with eagle reproductive problems.
[Spann, JW, RG Heath, JF Kreitzer, LN Locke. 1972. (Lethal and reproductive effects of mercury on birds) Science 175:328- 331]
#
Shooting, power line electrocution, collisions in flight and poisoning from eating ducks containing lead shot were ranked by the National Wildlife Federation as late as 1984 as the leading causes of eagle deaths.
[Anon. 1984. National Wildlife Federation publication. (Eagle deaths)]
VIII. Peregrine falcons
DDT was blamed for the decline in the peregrine falcon population.
#
The decline in the U.S. peregrine falcon population occurred long before the DDT years.
[Hickey JJ. 1942. (Only 170 pairs of peregrines in eastern U.S. in 1940) Auk 59:176; Hickey JJ. 1971 Testimony at DDT hearings before EPA hearing examiner. (350 pre- DDT peregrines claimed in eastern U.S., with 28 of the females sterile); and Beebe FL. 1971. The Myth of the Vanishing Peregrine Falcon: A study in manipulation of public and official attitudes. Canadian Raptor Society Publication, 31 pages]
#
Peregrine falcons were deemed undesirable in the early 20th century. Dr. William Hornaday of the New York Zoological Society referred them as birds that "deserve death, but are so rare that we need not take them into account."
[Hornaday, WT. 1913. Our Vanishing Wild Life. New York Zoological Society, p. 226]
#
Oologists amassed great collections of falcon eggs.
[Peterson, RT. 1948. Birds Over American, Dodd Mead & Co., NY, pp 135-151; Rice, JN. 1969. In Peregrine Falcon Populations, Univ. Of Wisconsin Press, pp 155-164; Berger, DD. 1969. In Peregrine Falcon Populations, Univ. Of Wisconsin Press, pp 165-173]
#
The decline in falcons along the Hudson River was attributed to falconers, egg collectors, pigeon fanciers and disturbance by construction workers and others.
[Herbert, RA and KG Herbert. 1969. In Peregrine Falcon Populations, Univ. Of Wisconsin Press, pp 133- 154. (Also in Auk 82: 62-94)]
#
The 1950's and 1960's saw continuing harassment trapping brooding birds in their nests, removing fat samples for analysis and operating time-lapse cameras beside the nests for extended periods of time), predation and habitat destruction.
[Hazeltine, WE. 1972. Statement before Secretary of State's Advisory Committee on United Nations Conference on the Human Environment, March 16, 1972; Enderson, JH and DD Berger. 1968. (Chlorinated hydrocarbons in peregrines from Northern Canada). Condor 70:149-153; Enderson, JH.. 1972. (Time lapse photography in peregrine nests) Living Bird 11: 113- 128; Risebrough, RW. 1970. (Organochlorines in peregrines and merlins migrating through Wisconsin). Canadian Field-Naturalist 84:247-253]
#
Changes in climate (higher temperatures and decreasing precipitation) were blamed for the gradual disappearance of peregrines from the Rocky Mountains.
[Nelson, MW. 1969. Peregrine Falcon Populations, pp 61-72]
#
Falconers were blamed for decimating western populations.
[Herman, S. 1969. Peregrine Falcon Populations, University of Wisconsin Press]
#
During the 1960's, peregrines in northern Canada were "reproducing normally," even though they contained 30 times more DDT, DDD, and DDE than the midwestern peregrines that were allegedly extirpated by those chemicals.
[Enderson, JH and DD Berger. 1968. (Chlorinated hydrocarbons in peregrines from Northern Canada) Condor 70:170-178]
#
There was no decline in peregrine falcon pairs in Canada and Alaska between 1950 and 1967 despite the presence of DDT and DDE.
[Fyfe, RW. 1959. Peregrine Falcon Populations, pp 101-114; and Fyfe, RW. 1968. Auk 85: 383-384]
#
The peregrine with the very highest DDT residue (2,435 parts per million) was found feeding three healthy young.
[Enderson, JH. 1968. (Pesticide residues in Alaska and Yukon Territory) Auk 85: 683]
#
Shooting, egg collecting, falconry and disruption of nesting birds along the Yukon River and Colville River were reported to be the cause of the decline in peregrine falcon population.
[Beebe, FL. 1971. The Myth of the Vanishing Peregrine Falcon: A study in manipulation of public and official attitudes. Canadian Raptor Society Publication, 31 pages; and Beebe, FL. 1975. Brit Columbia Provincial Museum Occas. Paper No. 17, pages 126-144]
#
The decline in British peregrine falcons ended by 1966, though DDT was as abundant as ever. The Federal Advisory Committee on Pesticides concluded "There is no close correlation between the declines in populations of predatory birds, particularly the peregrine falcon and the sparrow hawk, and the use of DDT."
[Wilson report. 1969. Review of Organochlorine pesticides in Britain. Report by the Advisory Committee on toxic chemicals. Department of Education and Science]
#
During 1940-1945, the British Air Ministry shot about 600 peregrines (half the pre-1939 level) to protect carrier pigeons.
#
Peregrine falcon and sparrow hawk egg shells thinned in Britain prior to the use of DDT.
[Redcliff, DH. 1967. Nature 215: 208-210; Redcliff, DH. 1970 J Applied Biology 7:67; and Redcliff, DH. 1967. Nature 215: 208-210]
IX. Brown pelicans
DDT was blamed for the decline in the brown pelican population.
#
Brown pelicans declined in Texas from a high of 5,000 birds in 1918 to a low of 200 in 1941, three years before the presence of DDT.
[Pearson TG. 1919. Review of reviews. Pp. 509-511 (May 1919); Pearson TG. 1934. Adventures in Bird Protection, Appleton- Century Co., p. 332; Pearson TG. 1934 (Discussion of 1918 survey) National Geographic pp. 299-302 (March 1934); Allen RG. 1935. Auk 52: p.199;]
#
Disappearance of the brown pelicans from Texas was attributed to fisherman and hunters. Gustafson AF. 1939. Conservation in the United States, Comstock Publ. Co., Ithaca, NY. (Repeated in U.S. Fish and Wildlife Service Report No. 1, 1970)]
#
Brown pelicans experienced no difficulty in reproducing during the DDT years.
[See Banks, RC. 1966. Trans San Diego Soc Nat Hist 14:173-188; and Schreiber RW and RL DeLong. 1969. Audubon Field Notes 23:57-59]
#
Brown pelicans did suffer reproductive problems following the 1969 Santa Barbara oil spill. Oil on eggs is a known cause of embryo death
[See e.g., National Wildlife Federation . 1979. Embryonic mortality from oil on feathers of adult birds. Conservation News, pp. 6-10 (October 15, 1979); Hartung, R. 1965. (Oil on eggs reduces hatch ability by 68 percent). J Wildlife Management 29: 872-874; King, KA 1979. (Oil a probable cause of pelican mortality for six weeks after spill). Bull Environ Contam. Toxicol 23:800-805; and Dieter, MP. 1977. (5 micro liters of oil on fertile egg kills 76 percent to 98 percent of embryos within. Interagency Energy-Environment Research and Development Program Report, pp 35-42]
#
Among brown pelican egg shells examined (72 percent), there was no correlation between DDT residue and shell thickness.
[Switzer, B. 1972. Consolidated EPA hearings, Transcript pp. 8212-8336; and Hazeltine, WE. 1972. Why pelican eggshells are thin. Nature 239: 410-412]
#
An epidemic of Newcastle disease resulted in millions of birds put to death to eradicate the disease.
[United Press International. "Newcastle disease epidemic in California (April 1972)] The epidemic among U.S. birds was caused by the migration of sick pelicans along the Mexican coast.
[Hofstad MC. 1972. Diseases of Poultry. Iowa State Univ. Press]
X. Bird populations increase during DDT years
Widespread declines in bird populations during the DDT years is a myth.
#
In congressional testimony, Charles Wurster, a biologist for the Environmental Defense Fund, noted the abundance of birds during the DDT years, referring to "increasing numbers of pheasants, quail, doves, turkeys and other game species."
[Wurster, C.F. 1969 Congressional Record S4599, May 5, 1969]
#
The Audubon Society's annual bird census in 1960 reported that at least 26 kinds of birds became more numerous during 1941 - 1960.
[See Anon. 1942. The 42nd annual Christmas bird census." Audubon Magazine 44;1-75 (Jan/Feb 1942), and Cruicjshank, AD (editor) 1961. The 61st annual Christmas bird census. Audubon Field Notes 15(2); 84-300]
#
Statistical analysis of the Audubon data bore out the perceived increases.
[White-Stevens, R. 1972. Statistical analyses of Audubon Christmas bird censuses. Letter to New York Times, August 15, 1972]
#
The white-tailed kite, a raptor, was "in very real danger of complete extirpation in the U.S." in 1935, but "by the 1960's, a very great population increase and range expansion had become apparent in California and the breeding range had extended through the Central American countries."
[Eisenmann, E. 1971. Range expansion and population increase of the White-tailed kite. American Birds 25(3):529-535]
#
Great increases inmost kinds of hawks during the DDT years were reported by the Hawk Mountain Sanctuary Association (Hawk Mountain, Pennsylvania).
[Taylor, JW. Summaries of Hawk Mountain migrations of raptors, 1934 to 1970. In Hawk Mountain Sanctuary Association Newsletters]
#
National forest studies from Wisconsin and Michigan reported an increase in nesting osprey productivity from 11 young in 1965 to 74 young in 1970.
[U.S. Forest Service, Milwaukee. 1970. Annual report on osprey status in national forests in Wisconsin and Michigan]
#
A study of fish-eaters at Funk Island (on the North Atlantic coast) reported that, despite diets contaminated with DDT, gannet and murres pairs increased by 1,500 percent and 10,000 percent from 1945 to the early 1970s.
[Bruemmer, F. 1971. Animals Magazine, p.555, April]
#
Herring gulls reportedly increased from 2,000 pairs in 1941 to 35,000 pairs in 1971. Ironically, the Massachusetts department of Natural resources permitted the Audubon Society to poison 30,000 of the pairs on Tern Island. The Audubon-ers preferred terns. Audubon Society scientist William Drury stated, "it's kind of like weeding a garden."
[Graham, F. 1985. Audubon Magazine, p.17, January 1985]
#
Some birds multiplied so well during the DDT years that they became pests:
*
6 million blackbirds ruined Scotland Neck, North Carolina in 1970, polluting streams, depositing nine inches of droppings on the ground and killing the forest where they roosted at night.
[Associated Press, March 18, 1970]
*
77 million blackbirds roosted within 50 miles of Ft. Campbell, KY increasing the risk of histoplasmosis in humans.
[Louisville Courier-Journal, December 1975.]
*
Ten million redwings were reported in a small area of northern Ohio.
[Graham, F. 1971. Bye-bye blackbirds? Audubon Magazine, pp. 29-35, September]
*
The Virginia Department of Agriculture stated, "We can no longer tolerate the damage caused by the redwing ... 15 million tons of grain are destroyed annually enough to feed 90 million people."
[Bulletin of the Virginia Department of Agriculture, May 1967]
*
The phenomena of increasing bird populations during the DDT years may be due, in part, to (1) fewer blood-sucking insects and reduced spread of avian diseases (avian malaria, rickettsial-pox, avian bronchitis, Newcastle disease, encephalitis, etc); (2) more seed and fruits available for birds to eat after plant-eating insects were decimated; and (3) Ingestion of DDT triggers hepatic enzymes that detoxify carcinogens such as aflatoxin. |
