In the notoriously wrong and misleading “100 things you should know about DDT” posted by pro-DDT, anti-wildlife Steven Milloy of “Competitive Enterprise Institute” and Fox News fame, based on the foggy rant of Dr. Gordon Edwards, we get these two misleading claims:
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]
99. The Audubon Society’s annual bird census in 1960 reported that at least 26 kinds of birds became more numerous during 1941 – 1960. [See Anon. 1942. The 42nd annual Christmas bird census.” Audubon Magazine 44;1-75 (Jan/Feb 1942), and Cruicjshank, AD (editor) 1961. The 61st annual Christmas bird census. Audubon Field Notes 15(2); 84-300]
100. Statistical analysis of the Audubon data bore out the perceived increases. [White-Stevens, R. 1972. Statistical analyses of Audubon Christmas bird censuses. Letter to New York Times, August 15, 1972]
Those claims are false with regard to bald eagles.
The careful citations offered by Milloy and Edwards simply do not exist; if the source exists, the source does not say what is claimed by these guys. (Don’t take my word for it; go see for yourself.)
Audubon never suggested, in any forum, that their famous Christmas Bird Count had shown increases in eagles. Most other species showed no increases, either. I spent a couple of days at the library of Southern Methodist University reviewing every issue of Audubon Magazine from 1941 through 1974, and found not a single article suggesting anything other than declining eagle populations in the lower 48 states (Alaska eagles were not untouched by DDT, but were not so seriously affected; and as you will see below, the first counts of Alaska’s eagles did not occur until after 1950, so the addition of numbers from Alaska counts do not indicate an increase in U.S. population of eagles.)
I also reviewed each bird count, usually published in a separate booklet with the March issue of Audubon in that time. While raw numbers increased, that was clearly due to increases in people observing. At no point did any ornithologist or Audubon member suggest eagles were in recovery, from 1941 through 1972.
That’s a long explanation, unsuitable for quick discussion on blogs, and wholly too much for a 140-character Tweet. My experience with Milloy and his followers is that they will say my analysis somehow errs, though they cannot offer any real analysis from any other source that isn’t just a misreading of the raw bird count.
I wrote the Audubon Society, and asked them to respond to the claim. At first the press office thought the claims so bizarre that they didn’t think a reply necessary. I sent them a half-dozen links to other documents that cited Milloy and Edwards. Delta Willis at Audubon took the claims to officials of the bird count.
Geoff LeBaron, Director of Audubon’s Christmas Bird Count sent the following reply (posted without correction).
See also the footnote from Audubon Chief Scientist Gary Langham appended to the end of the e-mail.
Sent: Friday, May 10, 2013 10:21 AM
To: Willis, Delta; Langham, Gary; Dale, Kathy
Subject: RE: DDT and effects on birds, and Audubon Christmas bird count
From the 1930s through 1970s there was a tremendous growth in the number of Christmas Bird Counts, from 203 total counts in the 30th CBC to 1320 counts in 80th CBC. The number of observers on those counts rose from 679 in 30th to 32,322 in the 80th Count. That is a tremendous increase in effort as well as geographic coverage, and more people in more areas are going to count more Bald Eagles, even if the populations are [were] declining.
A second major factor is that during that period many CBCs were started with the specific goal of censusing wintering Bald Eagles. Thus we were targeting the areas where eagles were wintering, and thus tallying a much greater percentage of the total population.
Thirdly, there were only two individual CBCs conducted in Alaska prior to the late 1950s. Bald Eagle populations never suffered dramatically in Alaska [from DDT?], and their numbers were always much higher there. Since the late 1950s there has been a tremendous growth in the number of counts in Alaska—again, with some of these counts targeting areas where wintering eagles congregate even in the thousands. These counts added in Alaska can contribute greatly to the total number of Bald Eagles in each season’s CBC.
Thus even while Bald Eagle populations were plummeting in the lower 48 states (outside of Florida) CBC [Citizen Science] efforts were greatly increasing, and in fact targeting monitoring Bald Eagles. That is why both the raw number of eagles and the numbers when weighted for observer effort went up when you pull CBC data for Bald Eagle during the decades of heavy DDT use.
It’s still educational to look at raptor numbers in CBC data in the years following the banning of the use of DDT in the US. Many species of raptors show a rapid rebound in numbers after the mid-1970s…and Bald Eagles also dramatically increased.
Per Dr. Gary Langham, Audubon Chief Scientist: Audubon scientists are careful to include levels of participation and geographic coverage in all analyses. Fortunately, we have tracked both of these aspects since the CBC was started and so it is straightforward to adjust for their impacts.
Bird counts do not show that eagles were out of trouble during DDT years, roughly 1946 through 1972; especially they do not show that bald eagle populations increased.
Explanation of the Christmas Bird Count in four minutes, by Chan Robbins.
Nota bene: Yes, this has sat in my “to be published” box for too long. It was scheduled for publication, but it appears I had not hit the “publish at scheduled time” button. My apologies to readers, and especially to Audubon’s scientists and press people.