Canadian wildfire smoke covers Minnesota, alert issued until noon Wednesday

MPR News helps you turn down the noise and build shared understanding. Turn up your support for this public resource and keep trusted journalism accessible to all. 

Turn Up Your Support

(AP)  Birds that once flourished in suburban skies,
including robins, bluebirds and crows, have been devastated by West
Nile virus, a study found.
    

  Populations of seven species have had dramatic declines across
the continent since West Nile emerged in the United States in 1999,
according to a first-of-its-kind study. The research, to be
published Thursday by the journal Nature, compared 26 years of bird
breeding surveys to quantify what had been known anecdotally.

      "We're seeing a serious impact," said study co-author Marm
Kilpatrick, a senior research scientist at the Consortium of
Conservation Medicine in New York.

      West Nile virus, which is spread by mosquito bites, has infected
23,974 people in confirmed cases since 1999, killing 962, according
to the Centers for Disease Control and Prevention.

      But the disease, primarily an avian virus, has been far deadlier
for birds. The death toll for crows and jays is easily in the
hundreds of thousands, based on the number dead bodies found and
extrapolated for what wasn't reported, Kilpatrick said.

      It hit the seven species - American crow, blue jay, tufted
titmouse, American robin, house wren, chickadee and Eastern
bluebird - hard enough to be scientifically significant. Only the
blue jay and house wren bounced back, in 2005.

      The hardest-hit species has been the American crow. Nationwide,
about one-third of crows have been killed by West Nile, said study
lead author Shannon LaDeau, a research scientist at the Smithsonian
Migratory Bird Center in Washington. The species was on the rise
until 1999.

      In some places, such as Maryland, crow loss was at 45 percent,
and around Baltimore and Washington, 90 percent was gone, LaDeau
said.

      While crows are scavengers and often disliked, they play a key
role in nature by cleaning up animal carcasses, LaDeau noted.
Researchers will next look into what species benefit from the
disappearance of crows.

      Researchers noted the die-offs came in patches, with many in
some places and none in others. Maryland appeared to be the
epicenter of bird deaths, though that was partly because the data
were not as good from New York, where the virus first hit, LaDeau
said.

      Chickadees, Eastern bluebirds and robins in Maryland were 68
percent, 52 percent, and 32 percent below expected levels in 2005.
Tufted titmouse populations in Illinois were one-third of what they
were expected to be.

      "It tends to be more suburban areas. Some of the common
backyard species including the blue jays, the robins, the
chickadees have suffered significant declines," LaDeau said.
"That heavily packed urban corridor is a bad place to be a bird.
The reason for that is that the mosquito prefers human landscape.
They do very well in suburbia."

      The birds act as an early warning system for humans, said Wesley
Hochachka, assistant director of bird population studies at Cornell
Lab of Ornithology.

      "If you start seeing crows dying and dying in numbers, that
means there could be a human outbreak," said Hochachka, who was
not involved with the study.

      The researchers looked at 20 species that were regularly counted
each breeding season and found that populations of 13 species were
not down because of West Nile. Biologists say they have seen other
species with many deaths, including owls, hawks, sage grouse and
yellow-billed magpies, but there are no breeding surveys to
quantify how bad the problem has been.

      Although entire small clusters of crows were "wiped out by West
Nile virus in a single season," Greg Butcher, director of bird
conservation at the National Audubon Society, remained hopeful.

      "All of those (bird populations) have the capacity to
rebound," he said.

Gallery

Populations of seven species have had dramatic declines across
the continent since West Nile emerged in the United States in 1999,
according to a first-of-its-kind study.

Bird surveys show West Nile virus devastated crows, robins, other birds in suburbia

Go Deeper.

Like this?