Bald eagles still not saved by DDT ban…

… no matter how many times the myth is repeated.

Today’s hapless echo of the DDT-bald eagle myth is reporter Scott Richardson of Bloomington, IL’s Pantagraph.com, who wrote:

Bald eagle numbers were plummeting when I was growing up not far from Starved Rock State Park.

The birds were listed as endangered until after the feds banned DDT. The agri-chemical had found its way into the food chain, first into the fish, then into the eagles that ate them. Egg shells were weakened so much they broke when mature eagles tried to keep them warm.

Today, the birds have rebounded. It’s a joy to see them wintering on the eagle refuge on Plum Island across from Starved Rock State Park. Many can be found there during the cold months when they are forced southward from Wisconsin, Michigan and Canada to find open water to feed. The colder the winter, the more eagles turn up there…

But as JunkScience.com readers know from “100 Things You Should Know About DDT“, DDT had nothing to do with the near demise of the bald eagle, and DDT’s ban had nothing to do with the rebound in bald eagle population:

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 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]

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)]

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5 responses to “Bald eagles still not saved by DDT ban…

  1. When did the Fish & Wildlife Service ever make a public announcement that DDT was not the cause of the decline of the bald eagle? Your average Joe 6-Pak doesn’t read the scientific publications where their research results are published.

  2. Not just “Joe 6-Pak”s, most of my supposedly well educated friends and acquaintances believe DDT was. I don’t know how in this age of a hard enviro-leftist press, the general public will ever know. Depressing.

  3. Well, I’ve yet to hear a GOP candidate mention DDT, which, though irrelevant to California condors and bald eagles, might just fight back the huge problem of malarial mortality if applied rationally. And there are plenty of other pests, such as some kinds of fruit flies, that we could much more safely fight with DDT than the politically correct alternatives.

  4. You can look at the Audubon Xmas Count data here.
    http://audubon2.org/cbchist/table.html
    Plug in Bald Eagle, 1920>2011 & United States, click make table, then when that shows convert to graph.
    DDT was only discovered in 1939. What you will find is that there is a small but steady rise in Bald Eagles counted by “party hours”. So since DDT was discovered in 1939, Bald Eagles populations have continued to grow.

  5. It seems to me that a better explanation for thinning eggs in the 1960s and 70s was that a far larger percentage of the breeding pairs were younger and smaller birds. Smaller birds and younger birds have thinner eggs. Younger birds also are far less successful raising young until they are old enough to be off on their own — either by accidently breaking their own eggs or by not properly protecting their nest/young.. (Anyone who has watched a pair of young doves or robins in their backyard tree can vouch for the fact that they are FAR more likely to be unsuccessful in the spring than they are later in the summer once they have matured a bit… but Eagles can’t normally lay eggs 2 or 3 times a year like doves or robins often do.

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