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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]
And here is some general information with regard to birds, thin eggs, and DDT.
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]
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.[/B][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. ]
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