Too bad knowledge about DDT doesn’t soar, too.
Tom Hanson of KDLT.com reports:
It wasn’t long ago, that getting a glimpse of our nations symbol, the bald eagle, was almost impossible.
The birds of prey were nearly extinct in the lower 48 states. However, since a ban on pesticides like DDT and a crack down on poaching, bald eagles have made a remarkable a comeback, especially in parts of South Dakota…
As JunkScience.com readers know from “100 Things You Should Know About DDT“, bald eagles were “decimated” long before DDT came along:
66. Bald eagles were reportedly threatened with extinction in 1921 — 25 years before widespread use of DDT. [Van Name, WG. 1921. Ecology 2:76]
67. Alaska paid over $100,000 in bounties for 115,000 bald eagles between 1917 and 1942. [Anon. Science News Letter, July 3, 1943]
68. The bald eagle had vanished from New England by 1937. [Bent, AC. 1937. Raptorial Birds of America. US National Museum Bull 167:321-349]
69. 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]
70. 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]
71. 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 72. 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]
73. 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]
74. 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]
75. 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]
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]
77. 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)]
With all the mosquitoes in Alaska, you can say that with a straight face? Where do eagles go to winter? In the southern 48 states. What is one of the eagles major food groups in Alaska? Salmon. Where do salmon spend most of there lives? In the ocean, the final resting place for most of the contaminants we release! Does DDT bio concentrate up the food chain? You betcha!!
Gregg M, you have fallen into the post hoc, ergo propter hoc fallacy. Eagles came back after hunting was banned. DDT was never used to any extent in Alaska, but eagles were vanishing due to hunting and random killings. once these were outlawed, the eagles came back in huge numbers. it was similar in northern Canadian areas.
Yep, then you would know they didn’t start their come back until after DDT was banned!
The main threat to bald eagles currently appears to be wind farms.