Keeping an Eye on Eagles

  • The bald eagle was protected by the Endangered Species Act for 40 years, but researchers are still finding toxic chemicals in the eagles' plasma. (Photo by William Bowerman)

The bald eagle came close to extinction
before strong measures were taken to help pull
it back. The eagle was protected by the Endangered
Species Act for 40 years. And the government banned
toxic compounds such as DDT that caused damage to the
eagles’ eggs. Bob Allen caught up with researchers
who are monitoring the health of the birds. They’re
finding the birds are still being exposed to toxic
chemicals:

Transcript

The bald eagle came close to extinction
before strong measures were taken to help pull
it back. The eagle was protected by the Endangered
Species Act for 40 years. And the government banned
toxic compounds such as DDT that caused damage to the
eagles’ eggs. Bob Allen caught up with researchers
who are monitoring the health of the birds. They’re
finding the birds are still being exposed to toxic
chemicals:


We’re on a steep, heavily wooded hillside about a mile above a
barrier dam on the Muskegon River in Michigan. The land is part of a private
church camp. So, human intrusion on the site is low. And the
pond behind the dam provides plenty of food for eagles rearing
their young.


Once every five years researchers are permitted to come here and
take young birds from the nest.


“Usually we try to keep people about a quarter mile away from the
nest. And that way we don’t have human disturbance that
would cause them to fail.”


Bill Bowerman is a wildlife toxicologist from Clemson
University. He first became part of this eagle survey as a grad
student at Michigan State more than 20 years ago, about the time
researchers began taking blood and feather samples.


Wildlife veterinarian Jim Sikarskie says eagles sit atop
the aquatic food chain, so any contaminants in the ecosystem
eventually show up in them:


“The contaminants that are in the plasma from the blood and
from the feathers then help us evaluate the quality of the water in
the area around the nest. So we do birds from different watersheds
every 5 years as part of the water quality surveillance plan.”


The nest is a tangled mass of twigs in an aspen tree swaying in a
strong breeze about 60 feet off the ground. As the research team
approaches, the female lifts off and begins to circle and squawk
just above the tree-tops.


They lay out syringes and test tubes on the ground. Walter
Nessen gets ready to climb the tree. He’s worked with
Bowerman monitoring sea eagles in his native South Africa.


Walter buckles into his harness and straps a pair of climbing
spikes to his boots. He has the kind of wiry strength and agility
that makes for a good climber. He prefers not to use gloves to
handle the eaglets because he relies on a sense of feel between
his hands and their legs:


“Immature birds, nestlings, are quite delicate because their
feathers are not hard-pinned. In other words, there’s still
blood circulating inside the feathers as it’s growing. One has
to be careful not to bend them or break them because they
will not develop further. That’s the most important thing.
The other thing is you need to take care the birds have big
claws. It’s one of the first things developing on the birds so
they can attack you and claw you and scratch you and that
kind of thing.”


Walter wraps his climbing rope, really a polyester-covered steel
cable, around the trunk of the tree, locks it into his harness and up
he goes.


First he checks nestlings to be sure they’re old enough and in
good condition before lowering them down in a special padded
“eagle bag.”


With young eagles on the ground, everyone becomes hushed and
businesslike. Bowerman writes down the eaglet’s weight and
other measurements. They’re four to five pounds with some
down-like feathers still clinging to them. Most prominent are
their dark beaks and yellow-orange claws.


Sikarskie carefully drops a cloth hat over an eaglet’s head to keep
the bird calm. Then, he talks a young grad student through
taking her first blood sample from the underside of a delicate
wing.


The two nestlings are examined for parasites. Then, they’re leg
banded, tucked gently back in the bags and hoisted aloft. They’re
out of the nest for maybe fifteen minutes.


Places like this, far upriver from the Great Lakes, were refuges
for eagles back in the DDT era. Eagles survived here because
fish couldn’t pass above barrier dams on the rivers and carry their
toxic burden with them, and Bowerman says the difference is still
noticeable today:


“If you live along the Great Lakes you still have higher levels
of PCBs. You still find DDE, which is the egg shell thinning
compound that caused the eagle’s decline in the first place. If
you’re in an area like this which is upstream of the Great
Lakes, there’s much less level in these inland birds.”


Eagle research in Michigan extends back 47 years.
Bowerman calls it the oldest continuous wildlife survey in the
world. It’s a record that documents the recovery of a species in
trouble, but sometimes the information has a more immediate
impact.


Bowerman says some years ago, tests on baby eagle’s blood
from Michigan showed a spike of an unknown chemical. Lab
tests found it to be from a product called Scotch Guard, a stain
repellent for fabric produced by the 3M Company.


When told about it, 3M hired Bowerman’s professor, John Geise,
to find out how widespread the compound was:


“John’s lab went all across the world collecting tissues of
different wildlife species. And they found it world-wide. And
that’s why 3M took scotch guard off the market.”


Bowerman worries that monitoring efforts will slack off when
bald eagles are off the Endangered Species list, and that new
contaminants will be missed. But he can’t help being inspired
by the birds’ recovery:


“Does it make you any more alive to watch that beautiful
eagle soaring around? And it’s really neat to see how many
there are now. So this is just spectacular.”


For the Environment Report, I’m Bob Allen.

Related Links

GAUGING MANKIND’S ECOLOGICAL FOOTPRINT

In the wake of the World Summit on Sustainable Development in Johannesburg, South Africa, there’s been a lot of talk about how to balance human needs with the health of the planet. Ecologists have been trying to measure the impact of humans on the environment for a number of years, with some sobering results. The Great Lakes Radio Consortium’s Daniel Grossman went to the New York Botanical Garden recently to gauge mankind’s ecological footprint:

Transcript

In the wake of the World Summit on Sustainable Development in Johannesburg, South
Africa, there’s been a lot of talk about how to balance human needs with the health of the
planet. Ecologists have been trying to measure the impact of humans on the environment
for a number of years, with some sobering results. The Great Lake Radio Consortium’s Daniel Grossman went to the New
York Botanical Garden recently to gauge mankind’s ecological footprint.


[Rain forest sounds, misters, tinkling of water, rain falling on leaves]


To get a good sense of the impact humans are having on earth, you could travel for weeks
on intercontinental plane flights, river boats and desert jeeps. Or, as Columbia University
biologist, Stuart Pimm suggested, visit a botanical garden. There, under the glass and
ironwork of a conservatory, Pimm says you can see a resource that humans are
over-using – Earth’s most important resource, its plant-life.


“We’re sitting in the rain forest here at the New York Botanical Society. And it’s a riot of
green.”


Professor Pimm says here beneath the misters in the Tropical Rain Forest Gallery is a
good place to start a whirlwind tour of Earth’s greenery. The air is heavy with moisture
and sweet-smelling.


“Rain forests are some of the most productive parts of the planet. They grow extremely
quickly and they are therefore generating a lot of biological production.”


What Pimm calls biological production most of us know as plant growth. Biologists say
all this green growth in tropical forests and elsewhere on Earth is the foundation upon
which all life rests.


“Everything in our lives is dependent upon biological productivity – everything that we
eat, everything that our domestic animals eat.”


And everything that every other animal eats as well. In a recent book, Pimm painstakingly
tallies up how much biological productivity we use. He starts with the rain forest. In the
last 50 years, loggers and settlers have cut down 3 million square miles of lush tropical
forests. Much was cut down for subsistence agriculture, a purpose Pimm says it serves
poorly.


“Although the tropical forest looks rich and productive, it is a very special place. And
when you chop that forest down the areas that replace it often become very, very much
less productive.”


[Sound of walking around conservatory]


Pimm speaks of the toll on greenery of cities and roads and of land converted to farming
in temperate regions such as the U.S. Midwest. Then, trekking along the botanical
garden’s gravel paths, he leaves behind the tropical mists and steps into the dry heat of a
Southwestern desert. Deserts and other dry lands are not very productive, but they
account for a substantial fraction of Earth’s land surface. Most of it is grazed by flocks of
sheep, goats, camels and cattle, often causing severe damage to vegetation. When these
uses are added to the other impacts of humanity on earth’s bounty, the results are
surprisingly large.


“What silence has shown is that we are taking 2/5ths of the biological production on land,
a third from the oceans. And that of the world’s fresh water supply, we’re taking half.”


[Fade out sound of conservatory. Fade up sound of Texas frogs.]


[Sound of plane engines]


Frogs and toads croak out a spring mating ritual in a concrete drainage ditch. Nearby, a
pilot practices maneuvers in a small plane occasionally drowning out the amphibian
serenade. Living in culverts, sharing the night with droning engines, these wild animals
are never completely free of human influences. From his Stanford University office,
Professor Peter Vitousek says wherever you look, the din of human activities is
interrupting and crowding out other species. Vitousek made one of the first attempts to
tally the impact of people on plant productivity in 1985.


[Frogs fade out in time for Vitousek’s act]


“The message to me was that we are already having a huge impact on all the other species
because of our use of the production of Earth and the land surface of Earth. That’s not
something that our models predict for some time in the future or something that we’re
guessing at on the basis of fairly weak information. It’s something that we’re clearly
doing now. That’s already happening.”


Many ecologists say this conclusion is beyond doubt. What they can’t say is whether
human domination of so much of nature’s output is good or bad. University of Minnesota
Professor David Tilman says as a member of the human race himself, he appreciates the
comforts in clothing, shelter and food our lifestyles buy us. And he acknowledges that the
survival of our own species is probably not imperiled – at least for the moment – by the
destruction of others. Still, he wonders if someday we’ll regret today’s resource intensive
practices.


“I think the more relevant question to me is, ‘Are we doing this wisely?’ ‘Are we wisely
appropriating the resources of the world?’ So, my concern is that we live in a balanced
way – a way that is sustainable through generations – that we leave our children and
grandchildren the same kind of world that we have.”


An expert on the impacts of agriculture, Tilman says we’re using up more resources than
can be replaced. He says if we don’t grapple with these important issues now, by the time
the human population reaches eight to ten billion or so people later this century, it might
be too difficult for us to do enough to save the planet’s life as we know it today.


For the Great Lakes Radio Consortium, I’m Daniel Grossman.

Zoo’s Import Captive Breeding Technique (Part 1)

  • Ann van Dyk isthe director and owner of the De Wildt Cheetah Center in South Africa. Her efforts to breed cheetahs in captivity have been recognized as thechief reason the cheetah is no longer on the endangered species list.

Zoos in North America have been working with
a small farm in South Africa to save one of the
fastest animals on earth. In the first report of a
two-part series… the Great Lakes Radio
Consortium’s Lester Graham reports… the effort
has helped restore populations of cheetahs in the
wild and in zoos:

Questioning the Need for Captive Breeding (Part 2)

  • A pair of cheetahs in a gamepark in Swaziland are protected from hunters. However, there are few places left in the wild for the sleek cats.

Although the cheetah was removed from the endangered species
list more than a decade ago… zoos are still breeding the animal in
captivity. In the second report of a two part series… the Great Lakes
Radio Consortium’s Lester Graham reports… along with a cheetah center
in Africa… the zoos plan to keep producing cheetahs in case something
happens to the animal in the wild: