Conservation: Grouse & West Nile Virus
The alarming effects of West Nile Virus in ruffed grouse populations and what hunters can do for conservation.
BY JOE HEALY
When ruffed grouse hunters talk about reduced numbers of birds, they often cite maturing cover, land development or poor nesting conditions. Now there is s new threat to one of the country’s favorite gamebirds: West Nile Virus.
West Nile Virus (or West Nile Fever) is a viral infection transmitted by mosquitoes typically to birds but also to other animals, including bats, horses, dogs, squirrels and even humans. The infection can result in inflammation (encephalitis or meningitis) of the brain or spinal cord. The disease doesn’t occur in every animal bitten by an infected mosquito, but those that are affected exhibit signs of lethargy or incoordination. Because the infection attacks the nervous system and vital organs, sometimes it kills; other times the animal recovers. The occurrence of West Nile Virus (WNV) in small birds like ruffed grouse is alarming, because the disease quickly can be fatal. (In humans West Nile can cause flu-like symptoms, and some people have died—most commonly the elderly.)
"The tendency is to give up. I hear it repeatedly from hunters in Pennsylvania and other states: ‘Nothing we can do now.'"
In 2016 the Centers for Disease Control and Prevention reported that WNV antibodies were detected in gamebirds such as chukar and ring-necked pheasants, though the disease is not known to kill those birds. West Nile reportedly has accounted for many sage-grouse fatalities, and some waterfowl and avian predators such as owls, hawks and even bald eagles have tested positive for the disease.
In 2015 the Pennsylvania Game Commission (PGC) began studying the impacts of WNV on ruffed grouse populations. An initial laboratory study showed that 40 percent of infected chicks died quickly of the disease, with another 50 percent showing lesions and inflammation in major organs. Fortunately, data from hunter-harvested birds seem to indicate that grouse show higher promise of surviving West Nile when they live in high-quality habitat with ample food supplies.
The leading PGC biologist for grouse, Lisa M. Williams, said that many hunters feel helpless against West Nile once it’s detected in grouse: “The tendency is to give up,” she said. “I hear it repeatedly from hunters in Pennsylvania and other states: ‘Nothing we can do now.’ But in Pennsylvania we’ve had a couple years more to think about this issue, since our early studies in 2015.”
In license years 2015 and ’16, the PGC conducted a program of large-scale grouse-blood collection from successful hunters. In license year 2017 collection on a more targeted and smaller scale was done. The state’s next grouse-blood-collection likely will occur in about five years, to determine if WNV antibody levels in the grouse population have changed.
"I’m always careful to say, right now it appears that abundant and high-quality habitat in a prime-forest-community type seems key."
According to Williams: “Those of us who are passionate about grouse have done our grieving, and now we’re moving straight to action. We have to work smart, not just hard, on habitat improvement. We need to figure out where healthy grouse are and where disease isn’t.” She offered a rallying cry: “Now is not the time to give up. Now is the time to get busy.”
Williams says biologists have to think about finding grouse with West Nile Virus-positive antibodies—“birds that have been exposed and survived and are likely resistant for life. That’s a population to work with! Put high-quality habitat where those birds are. Put enough of it scattered across that immediate landscape, and the youngsters from that population can safely disperse and establish new territories.”
Equally important is improving habitat where West Nile Virus–carrying mosquitoes are less active. “Are there landscape barriers and thresholds we can work with—factors that limit vector [mosquito] populations?” Williams said. “Elevation? Slope? Distance from water? Distance from forest edge? We’re studying that now. If we can crack the code on West Nile Virus, then we know where to put habitat. We really need to start focusing on ways to stack the deck back in favor of grouse. Our preliminary data tell us that the proportion of birds showing West Nile antibodies [i.e., survivors] is higher in areas of abundant and high-quality habitat in a high-quality forest type.”
She says high-quality habitat helps grouse weather the threat of West Nile, because it keeps birds in good physical condition by offering a variety of year-round food sources that are easily accessible and provides dense cover, so that weakened or sick birds have security while they recover.
According to Williams: “I’m always careful to say, right now it appears that abundant and high-quality habitat in a prime-forest-community type seems key. In the northern hardwood areas of Pennsylvania we see hunter flush rates recover more quickly after a bad West Nile Virus year. Habitat abundance at a large landscape scale is also important: You need lots of birds to make lots of chicks to replace lots of birds lost to West Nile Virus . . . and you’ll only get that recipe if you have a lot of habitat scattered nicely across the landscape.”
Biologists in Pennsylvania and elsewhere have not reported any cases of humans or bird dogs contracting West Nile through consumption of ruffed grouse or any other wild game. But the prevalence of West Nile appears to be expanding.
What You Can Do
► For current information on West Nile Virus, the Pennsylvania Game Commission website has the most complete and up-to-date research on the disease in ruffed grouse. Hunters interested in other states’ findings should consult those states’ websites.
► If you kill a grouse and suspect that it may have WNV, Pennsylvania biologist Lisa Williams suggests labeling the bird with the date, location, and your name and contact info and freezing it. Then contact your state’s wildlife agency for instructions. This applies to wild turkeys and other gamebirds as well. Any information gathered about West Nile Virus will help biologists form their actions plans. —J.H.
In December the Michigan Department of Natural Resources issued a report reading: “Add ruffed grouse to the list of Michigan birds found to have the West Nile Virus. The Michigan Department of Natural Resources confirmed the presence of the viral infection in five birds collected from August through October. This is the first time West Nile has been discovered in the state’s ruffed grouse population even though the disease has been in Michigan since 2002.”
Virginia and Kentucky also reported finding grouse with WNV. New York found WNV antibodies in animals in the early 2000s, and passive surveillance continues there. In 2005 Minnesota tested grouse during the Ruffed Grouse Society National Grouse and Woodcock Hunt and found WNV antibodies. Check the game-and-fish websites of other Northeast, New England and Midwest states to find out current info.
Hunters can’t stop the disease. We can’t immunize every grouse or eradicate every mosquito carrying WNV. But we can help improve habitat, so that surviving birds, including those carrying West Nile antibodies, can recover and thrive.
For now, the best hope comes from focused research and the dedicated efforts of hunters to help improve habitat and therefore preserve grouse populations. Once again, as with many conservation challenges, this is a call to action for hunters to step up.