The brown pelican was not endangered by DDT.
In celebrating the recovery of the brown pelican population, the New Orleans Times-Picayune writes,
The brown pelican survived a brush with extinction, and the bird was declared healthy in 2009, 39 years after it was placed on the endangered species list. In the 1960s, the pelican had largely disappeared from the Gulf Coast, primarily because of decades of heavy use of the pesticide DDT in agriculture and mosquito control.
But a ban on DDT and efforts to protect pelican nesting sites led to a dramatic comeback for the Louisiana state bird.
Research in the late 1960s proved that DDT, ingested from the fish pelicans ate, caused eggshells to crack prematurely. The chemical was banned in 1972. In its absence, the osprey, the bald eagle and other fish-eating birds also made comebacks.
By November, 2009, the brown pelican population was estimated at about 650,000 in the Gulf Coast, Florida and California…
But the brown pelican had almost disappeared way before DDT came on the scene and then DDT had no effect on the pelican populations.
Check out the following from JunkScience.com’s “100 Things You Should Know About DDT“:
92. 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;]
93. 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)]
94. 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]
95. 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]
96. 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]
97. 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]