[tn-bird] Re: DDT Impacts on Birds
- From: "Rack Cross" <frogfarm@xxxxxxxxxxxxx>
- To: <tn-bird@xxxxxxxxxxxxx>
- Date: Wed, 28 Aug 2002 04:16:49 -0400
Thanks Bob for bringing the state info to my attention. Again, I find =
this topic a matter of intrigue and value as it relates to how we will =
respond to the next DDT type episode.
Indeed the abuse of DDT was cause for alarm, however, in PA, "For all =
hawks, the annual count showed an increase from 9,291 in 1957 to 20,196 =
in 1967. Since it was protected by the endangered species designation =
populations of the American Bald Eagle have increased significantly." =
"...191 0spreys in 1946, compared to 600 in 1970." D.L. Ray, Trashing =
the Planet. This passage also mentions an increase in Gulls along the =
East Coast during 1941 - 1971 and that another bird of prey, the =
Peregrine Falcon had been on the decline since 1890 probably due to =
habitat loss.
This is a very intresting contrast in data between Tennessee and =
Pennsylvania. Further, I have had distinct pleasure of viewing at =
relatively close range a Bald Eagle here at South Holston Lake, Bristol, =
TN. in the early 90's. Perhaps I was the benefactor of the hacking =
program, at any rate I am certainly opposed to any harmful event coming =
to our raptor's or other bird groups as I am opposed to accepting =
conventional wisdom as fact.
"Til we bird again
Rack Cross
Blountville, TN
Sullivan County=20
=20
-----Original Message-----
From: Bob Hatcher <bhatcher@xxxxxxxx>
To: TN-BIRD@xxxxxxxxxxxxx <tn-bird@xxxxxxxxxxxxx>
Date: Tuesday, August 27, 2002 9:58 PM
Subject: [tn-bird] DDT Impacts on Birds
The conventional wisdom is of course that DDT builds up at higher =
concentrations in birds at the top of the food chain. This includes the =
raptors and wading birds, which suffered major declines after DDT was =
introduced in the 1940's. Recovery only began after DDT was banned in =
1972 in the U.S. and in Canada in 1973, and requiring more years while =
DDT and its derivatives dissipated from the environment. =20
As an example, records of Reelfoot National Wildlife Refuge list 14 Bald =
Eagle nests for Reelfoot Lake in each of 1954 and 1955 (I estimate that =
roughly half that many nests were occupied throughout the nesting =
seasons, based on Albert Ganier's report during that era). After only =
one known STATEWIDE successful eagle nest in 1961 (at Lake Isom, 5 miles =
south of Reelfoot Lake), there were no known fledged Bald Eagles in =
Tennessee until 1983, when one young Bald Eagle fledged near Dover, =
Tennessee. The release of hacked Bald Eagles (287 in Tennessee during =
1980 - 2003) and a few other rare raptors has sped up the recovery of =
these species. Troy Ettel has reported that 76 young Bald Eagles have =
been recorded in 43 Bald Eagle nests in Tennessee during 2002 (compared =
to 60 young fledging from 36 nests in 1999). Late eagle nesting reports =
have usually been received well past this date.
The once huge heronries of Reelfoot Lake also virtually disappeared =
during these periods. Wading birds have obviously made comebacks since =
the late 1970's. In 1996, Dr. Fred Alsop provided the following two =
further examples (and more), as related to the Great Blue Heron and =
Great Egret of Tennessee:
Great Blue Heron - "The breeding colonies in West Tennessee decreased =
steadily since the early part of this century, but their decline has =
been most dramatic from the 1950's to the mid-1970's. At Reelfoot Lake =
in 1938 there were over 1000 active nests of 5 species of herons at =
"Cranetown" of which over 300 belonged to the Great Blue Heron. 1959 was =
the last big year for the colony with about 200 nests. By 1962 there =
were only 3 nests, and the following year there was none."=20
Great Egret - "Much reduced since the late 1930's and early 1940's in =
Tennessee. At Reelfoot Lake in the late 1930's the bird was very common; =
an estimate of 3500 on the lake was thought to be "conservative" and =
there were over 650 nests. By the early 1960's this colony and others =
had "crashed" and many were defunct. For more than a decade Great Egrets =
were not found nesting in Tennessee. They reestablished small breeding =
colonies in the late 1970's and these colonies continue to slowly grow."
Since songbirds are not at the top of the food chain, it would not be =
surprising that they would be relatively unaffected by DDT. However, =
the evidence is very convincing that DDT had a major negative impact on =
birds at the top of the food chain, at least in the United States. We =
can be thankful that there are now better alternatives than DDT for =
fighting mosquitoes and the West Nile Virus, which will be a challenge =
at best.
Bob Hatcher
Brentwood, Tennessee
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with 'unsubscribe' in the Subject field.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Topographical Maps located at http://topozone.com/find.asp
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Visit the Tennessee Ornithological Society
web site at http://www.tnbirds.org
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
TN-Bird Net Owner: Wallace Coffey, Bristol, TN
jwcoffey@xxxxxxxxxx (423) 764-3958
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