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sky overhead was full of them only four years ago. Now we seldom see any."
Here we have another instance of assertion being flatly contradicted by the
facts, for the very next year ornithologist Roger Tory Peterson described the
robin as "probably
North America's number one bird" in terms of numbers. The Audubon Society's
figures for annual bird
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counts bore him out, reporting 8.41 robins per observer in 1941 (pre-DDT) and
104.01 for 1960, representing a more-than twelve-fold increase during the
years when DDT use was at its highest. The corresponding figures for the eagle
and swallow were increases by factors of 2.57 (counts per observer
3.18, 8.17) and 1.25 (0.08, 0.10) respectively. This pattern was general for
most of the species listed, 202
showing 21 times more cowbirds, 38 times more blackbirds, and no less than 131
times more grackles, the average total count per observer being 1,480 in 1941
and 5,860 in 1960. Gulls became so abundant on the East Coast that the Audubon
Society itself obtained permission to poison 30,000 of them on Tern
Island, Massachusetts, in 1971. Wild turkeys increased from their rare status
of the pre-DDT years to such numbers that hunters were bagging 130,000
annually. Of the few species that did decrease, some, such as swans, geese,
and ducks, are hunted, while bluebirds are known to be susceptible to cold
winters.
Ironically, some of the areas where birds seemed to thrive best were those of
heaviest DDT use, such as in marshes sprayed to control mosquitos. Part of the
reason seems to be that DDT is also effective in reducing insects that
transmit bird diseases and which compete with birds for seeds and fruit.
But perhaps even more important, DDT triggers the induction of liver enzymes
that detoxify potent carcinogens such as aflatoxins that abound in the natural
diets of birds
None of this prevented any real or imagined decline in bird population from
being immediately attributed to pesticides. A severe reduction in eastern
ospreys turned out to be due to high levels of
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mercury in the fish upon which they fed and to pole traps set around fish
hatcheries blamed on DDT
even though reported as early as 1942. Alaska ospreys continued to do well
despite high DDT residues.
California brown pelicans increased almost threefold during the heavy DDT
years but experienced a sharp decline at the beginning of the seventies two
months after an oil spill at Santa Barbara surrounded their breeding island of
Anacapa (not mentioned in the reports of the state and federal wildlife
agencies). In 1969 the colony had been severely afflicted by an epidemic of
Newcastle disease transmitted from pelican grounds along the Mexican coast of
the Gulf of California (also not mentioned).
It was later established that helicopter-borne government investigators
collected 72 percent (!) of the intact eggs on Anacapa for analysis and
shotgunned incubating pelicans in their nests. DDT was also
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implied as being connected with the reduction of the Texas pelican, even
though the decline had been noted in 1939 and attributed to fishermen and
hunters.
The great eastern decline in the peregrine falcon was to a large degree due to
the zealousness of egg collectors who have been known to rob hundreds of nests
year after year, and then attribute the ensuing population collapse to the
encroachments of civilization. In 1969, "biologists" studying peregrines in
Colville, Alaska, collected fully one-third of the eggs from the colony and
then dutifully reported that only two-thirds of the expected number of falcons
subsequently hatched.
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Cracking Open the Eggshell Claims
But by the time of the 1971 hearings, the main allegation, still perpetuating
the fiction that a catastrophic fall in bird populations was taking place, had
become that DDT was the cause not as a result of immediate toxicity, but
indirectly through disruption of the reproductive cycle by the thinning of
eggshells. This again goes back to
Silent Spring
, which states (p. 120), "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." This was a reference to
experiments performed by James
DeWitt of the U.S. Fish and Wildlife Service, published in the
Journal of Agricultural Food and
Chemistry in 1956 (4: 10 pp. 853 66). The quail were fed 3,000 times the
concentration typically encountered in the wild. 80 percent of the eggs from
the treated group hatched, compared to 83.9
percent of the untreated controls, so the claim of a "few" was clearly false,
and the difference in results hardly significant. Moreover, 92.8 percent of
the eggs from the DDT-fed birds were fertile, compared to
89 percent from the controls, which reverses the impression created by the
quoted text. Also omitted was that DeWitt's study was actually conducted on
quail and pheasant. Of the pheasants, 80 percent of the eggs from the treated
birds hatched compared to 57.4 percent for the controls, and 100 percent of
the DDT birds survived against 94.8 percent of the control group.
A number of later studies were cited at the EPA hearings, purporting to
account for an effect
(major decline in bird populations) that wasn't happening. All of them are
examined in
Ecological Sanity
with more care and thoroughness, it would appear, than by the witnesses who
built their cases on them.
A 1969 experiment (Heath et al.) on mallard ducks, performed at the Patuxent
Wildlife Center at
Laurel, Maryland, reported that birds fed DDT and DDE (the major metabolic
residue from DDT
breakdown) suffered a mortality among embryos and hatchlings of from 30 to 50
percent. The first thing that struck Claus and Bolander upon reviewing the
paper was an enormous range of variation with the control groups that nobody
else had apparently objected to. For instance, the number of eggs laid per hen
in one control group was 39.2, whereas in another it was 16.8. This difference
alone was far greater than any of the differences said to be "significant"
among the experimental birds. The difference in live fourteen-day-old
hatchlings in the same groups was 16.1 versus 6.0, which again was greater (69
percent) than the 50 percent deficit in ducklings per hen reported for the
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birds fed the highest DDT diet.
When the variations among the controls are greater than the variations between
the control and experimental animals, it should be obvious that some factor
other than the test variable is operating (a bacterial infection, for
example), which affects both groups. Claus and Bolander conclude (p. 406):
On the basis of these absurd differences . . . the entire study becomes
meaningless, and all of the conclusions presented by the authors have to be
discarded." And (p.408)
"How this paper could have been passed for publication in
Nature is unfathomable, for even rapid scanning of the tables presented in the
article should have made it immediately evident to the referees that the data
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