On Page 120 of Silent Spring: Rachel Carson explains the lack of young birds by saying: “… [The reproductive capacity of the birds has been so lowered by some environmental agent that there are now almost no annual additions of young to maintain the race. Exactly this sort of situation has been produced artificially in other birds by various experimenters, notably Dr. James DeWitt of the U.S. Fish and Wildlife Service. Dr. DeWitt’s now classic experiments on the effects of a series of insecticides on quail and pheasants have established the fact that exposure to DDT or related chemicals, even when doing no observable harm to the parent birds, may seriously affect reproduction. … For example, quail into whose diet DDT was introduced throughout the breeding season survived and even produced normal numbers of fertile eggs. But few of the eggs hatched”[emphasis added].

Carson gives no indication of how many might be considered as “few eggs hatching.” Perhaps she thought that her readers would never see the rather obscure journal in which DeWitt’s results were published in 1956, the Journal of Agriculture and Food Chemistry. Otherwise, she surely would not have so badly misrepresented DeWitt’s results! The dosage he fed the quail was 100 parts per million in all their food every day, which was roughly 3,000 times the daily DDT intake of humans during the years of the greatest DDT use!

The quail did not just hatch “a few” of their eggs, as DeWitt’s data clearly reveal (Table 3). As the published data from DeWitt’s experiments show, the “controls” (those quail with no DDT) hatched 83.9 percent of their eggs, while the DDT-fed quail hatched 75 to 80 percent of theirs. I would not call an 80 percent hatch “few,” especially when the controls hatched only 83.9 percent of their eggs.

Carson either did not read DeWitt’s article, or she deliberately lied about the results of DeWitt’s experiments on pheasants, which were published on the same page. The “controls” hatched only 57.4 percent of their eggs, while the DDT-fed pheasants, (dosed with 50 ppm of DDT in all of their food during the entire year) hatched 80.6 percent of theirs. After two weeks, the DDT chicks had 100 percent survival, while the control chicks only had 94.8 percent survival, and after 8 weeks the DDT chicks had 93.3 percent survival while the control chicks only had 89.7 percent survival. It was false reporting such as this that caused so many leading scientists in the United States to take Rachel Carson to task.*

*The above was taken from: http://www.21stcenturysciencetech.com/articles/summ02/Carson.html

Here’s another good article about the impact of “Silent Spring”, showing how it was used by campaigners to have DDT banned rather than, as Carson recommended, have its use limited and questionned:
http://news.independent.co.uk/people/profiles/article2584181.ece

There’s a really nice discussion of “Silent Spring” and about Rachel Carson’s work on a 2002 Radio 4 programme. You can “listen again” at:

http://www.bbc.co.uk/radio4/history/greatlives/campbell_carson.shtml

There are really interesting comments on how effective she was an educationalist and campaigner, but I found the most moving part of this programme was a reading from part of the first chapter of “Silent Spring”

Worth a click and a listen!