Interns for Presque Isle State Park in Erie, Pennsylvania walk along a Lake Erie beach picking up dead birds. (Photo by Lester Graham)
Researchers are beginning to understand what’s killing thousands of
Great Lakes shorebirds. It might be part of a larger problem indirectly
caused by humans. The Great Lakes Radio Consortium’s Lester Graham
reports:
Transcript
We’ve been bringing you reports from the series, ‘Ten Threats to the Great Lakes’ which is now looking at the threat to beaches. Our guide through the series is Lester Graham. He reports that scientists are beginning to understand what’s killing thousands of Great Lakes shorebirds. It might be part of a larger problem indirectly caused by humans.
Researchers are beginning to understand what’s killing thousands of
Great Lakes shorebirds. It might be part of a larger problem indirectly
caused by humans. The Great Lakes Radio Consortium’s Lester Graham
reports:
Along parts of Lake Erie, Lake Ontario, and Lake Huron, large numbers
of dead birds and fish are washing up on shore. If they’re left there, the
disease that killed them can be passed on to other wildlife. That’s why
park officials such as Mike Mumau at Presque Isle State Park at Erie,
Pennsylvania ask their staff to watch out for the dead carcasses.
“Our interns do a great job. They’re the eyes of the staff that are out. So,
there’s probably three to four days a week that they’re out on the
beaches, checking to see if they have anything.”
Since 1998, untold numbers of fish and sometimes hundreds of dead
birds a year have washed up on just these eight miles of Lake Erie beach.
Eventually, researchers figured out the problem: type “E” botulism. It
slowly paralyzes the birds until the respiratory system shuts down. Most
of them don’t make it that long. They get so weak they can’t hold their
heads up out of the water and they drown.
(Sounds of walking and shovel)
Leslie Jones and her fellow interns are headed out to an area to pick up
some dead seagulls on the beach.
“When we’re out here doing migratory bird studies, we might see some
and then we pick them up as soon as possible. A lot of times, we get
radioed from different people like lifeguards and they have us come out
and pick them up so that the disease doesn’t spread throughout the rest of
the ecosystem.”
They find five dead birds rotting on the beach. They bury the maggots
because they could carry the botulism toxin and other birds might eat the
maggots. They shovel the bird carcass into a black plastic garbage bag.
“If they’re very fresh, this one, obviously not very fresh, but, if we get a
fresh one, we actually freeze them and they’re sent off to be tested
botulism, but, something like this we’ll just bag up until we can get them
incinerated to get rid of all the disease.”
The fresh carcasses are shipped to the National Wildlife Health Center in
Madison, Wisconsin.
There, Grace McLaughlin is among the researchers who are beginning to
put the puzzle together.
Here’s what they think is happening. The invasive species zebra mussels
and quagga mussels create huge mussel beds that begin a complicated
biological phenomenon. Organic matter collects there, and then decays. It
lowers the oxygen level in the immediate area of the mussel beds. Type
“E” botulism spores occur naturally, but when the oxygen level goes
down, they begin reproducing like crazy. The waste they produce is the
toxin.
“That toxin will accumulate in the organic matter as well as in the water
in the immediate vicinity of the mussel beds. As the mussels do their
filter feeding, they will accumulate the toxin in their tissue. They are not
susceptible to the toxin. However, when the fish start coming down
there and eating the mussels, they become intoxicated, lose their ability
to swim properly and become easy prey for the birds that come in.”
The fish that feeds on the mussels the most is another invasive species,
the round goby. Researchers made the connection when they noticed the
botulism started being a problem shortly after round gobies arrived in big
numbers.
The type “E” botulism toxin has killed tens-of-thousands of birds such as
cormorants, terns, loons, ducks, and seagulls.
Back at Presque Isle State Park, Mike Mumau says it’s terrible to see so
many birds die.
“We just do our best on our end to stop the botulism cycle. When we
can, provide samples, and also, keep it a positive recreational experience
for all our visitors. They don’t want to see birds decomposing and
rotting out on the beaches, so we’re pretty diligent with that.”
Researchers say that’s about the best that can be done. Since ocean-
going vessels brought zebra mussels, quagga mussels, and round gobies
to the Great Lakes, all three of the invasive species have flourished. It
will likely be a long time before we’ll ever begin to understand the full
extent of the damage to the native wildlife of the lakes.
For the GLRC, this is Lester Graham.
