Published Date: 2008-01-16 22:00:13
Subject: PRO/AH/EDR> Botulism, avian - USA: Great Lakes
Archive Number: 20080116.0210
BOTULISM, AVIAN - USA: GREAT LAKES
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: 15 Jan 2008
Source: WGNTV [edited]
Botulism and the infamous zebra mussel are blamed for killing birds
from gulls to loons by the thousands.
The bird die-off was obvious as soon as Gary Rentrop and his English
setter turned onto the Lake Michigan shore. The sugar-white sand,
long buried in the crushed gray shells of invasive mussels and mats
of rotting algae was now suddenly littered with dead birds.
"It was almost like a war zone of birds," said Rentrop, a Michigan
lawyer who recalled his November 2007 stroll along a Michigan beach.
Rentrop counted 80 carcasses on a remote mile of beach near Cross
Village, just a fraction of the estimated thousands of dead
mergansers, gulls, loons and other birds whose migration last autumn
2007 ended in deadly poisoning from Type E botulism on Lake Michigan.
The mounting toll on migrating birds has stoked fears among
researchers and ecologists that blame for the deaths lies with
invasive populations of zebra mussels and round gobies -- which
arrived in ballast tanks in the 1980s and 1990s -- spreading over the
Great Lakes and effectively creating a new food chain.
Zebra mussels and their deep-water kin, quagga mussels, filter
naturally occurring botulism and other toxins from the water. Gobies
eat the mussels, and birds, in turn, eat the gobies.
Scientists theorize this new food chain is concentrating botulism and
other toxins and passing them up to predators. The theory is the
subject of a handful of scientific papers and upcoming research proposals.
Whatever the mechanism of transmitting the botulism, scientists in
1999 counted 311 birds in Lake Erie that appeared to die of it. The
next year, they counted 8000, and the toll has remained in the
thousands in the Great Lakes every year since. And instead of fading
quickly as outbreaks did in decades past, the toxin has spread, 1st
through Lakes Erie and Ontario then to Huron. In 2006, Lake Michigan
was the most recent lake to be affected and by last autumn 2007 was
one of the hardest hit.
In spreadsheets, scientists have noted the fatal effects of the
annual outbreaks on more than 50 species of birds throughout the
Great Lakes, from bald eagles to lowly pigeons. The list names 16
species of ducks, 4 types of grebes and 6 types of gulls. It includes
the double-crested cormorant and 4 of Lake Michigan's tiny piping
plovers, a bird so threatened its nests get protection from police
tape and fences at Sleeping Bear Dunes National Lakeshore.
The deaths of many hundreds of loons have focused new urgency on the
now-annual die-offs that occur from summer to fall. Loons live in
small numbers, are slow to reproduce and are a symbol of northern wilderness.
The die-off that ended in November 2007 claimed an estimated 3500 to
8500 birds -- including the loons and plovers -- over hundreds of
miles of beach in 7 northern Michigan counties. It spread from an
estimated 2900 birds in 2006 along just 14 miles of shoreline at
Sleeping Bear Dunes, said dunes biologist Ken Hyde.
The die-off also sparked preparations for a sprawling and macabre
bird count in 2008 that will involve scores of volunteers combing
hundreds of miles of Lake Michigan beaches over the summer and fall
to add up, bury and haul off what are expected to be thousands more
poisoned birds and fish.
"We wish we weren't dealing with this," said Mark Breederland, who as
extension educator for the Michigan Sea Grant research program is
organizing the upcoming response. "We've got enough challenges on
Lake Michigan, but it's here. It's upon us."
The heightened threat to Lake Michigan became clear over the summer
, when shore birds began dying, possibly of picking maggots off
infected fish carcasses that washed ashore. Then came autumn.
"We were getting so many loons," said Thomas Cooley, a Michigan
Department of Natural Resources biologist who performed necropsies on
the birds. It takes 10 or 12 of the big birds to cover a laboratory
table, he explained. "When you have 2 or 3 tables covered with those,
it's pretty sobering to look at that."
Among the birds found dead was one of the most-studied loons in
Michigan, a venerable male with 4 boldly colored tags on his legs and
a name: C-3.
Each year since 1993, he had been observed at an Upper Peninsula pond
in the Seney National Wildlife Refuge, said Damon McCormick, a
biologist at Common Coast Research and Conservation who studied the bird.
Researchers knew C-3 had spent much of his life with the same female
loon on a secluded pond in a corner of the refuge and that for
unexplained reasons, he had recently left her for another loon on a
neighboring pond in the refuge.
They knew that he stayed behind at the new pond a few weeks this year
[presumably 2007] to supervise one late blooming chick as other loons
began their fall migration, which may have timed his migration
perfectly to a botulism plume and indirectly spelled his doom. To
their knowledge, C-3 had raised more than 15 chicks over the years
and only once let a chick drown, when its leg got caught on a
submerged log. For a loon, this made him a good father, researchers said.
The loon's body was found 1 Nov 2007 by an old friend, of sorts, on a
deserted, sandy crescent of Lake Michigan's north shore.
Biologist and Common Coast co-director Joe Kaplan had handled C-3 "4
or 5" times in 14 years, most recently in 2006. Kaplan was on his
last day of surveying bird carnage along the shore when he discovered the body.
"I remember specifically walking up to this bird," Kaplan said.
"There are thousands of thousands of birds that died on that lake,
and here's a bird that had a known history. I had a relationship with
this bird. It's an element of familiarity that you didn't want to find."
Adult loons return to their northern nesting grounds by early spring
about 93 percent of the time, McCormick said. This year ,
researchers will be watching for them anxiously. A decline in adult
population would almost certainly spell a decline among loons.
"We expect to see all our birds," McCormick said. "But based on
finding the C-3 male, there's a lot more trepidation of what we'll
find this spring ."
[Byline: James Janega]
[Images of zebra and quagga muscles may be viewed at:
Images of mergansers may be viewed at:
Images of loons may be viewed at:
Map of Great Lakes:
The reader is encouraged to read the information regarding botulism
in avians posted on ProMED-mail 20071207.3942. There is also
interesting insight into research regarding the mussels on
ProMED-mail 20080103.0031. - Mod.TG]