Providing High-Quality Habitat may be our Best Option to Protect Ruffed Grouse
by Ashley Peters
Bird hunters in Minnesota provided scientists with hundreds of ruffed grouse samples throughout 2018 and 2019. These samples were then tested for active West Nile Virus (WNV) infection and antibodies indicating infection with WNV. The results of that study were published earlier this year in The Journal of Wildlife Diseases.
The Centers for Disease Control and Prevention says that WNV is the leading cause of mosquito-borne disease in the U.S. Humans can catch WNV through mosquito bites, which can cause flu-like symptoms. However, WNV isn’t usually lethal for people. In birds, WNV infections have been known to frequently kill corvids, especially crows, as well as several other bird species. In the lab, ruffed grouse exposed to WNV do get sick.
Dr. Charlotte Roy, the study’s lead author with the Minnesota Department of Natural Resources (DNR,) said the study shows some birds can survive infection with WNV. A significant number of birds developed antibodies and survived, which is good news.
Most Sampled Birds Had Not Been Sick
The study’s authors worked with cooperating hunters to collect hearts, feathers and blood on filter strips from birds killed in the fall to examine exposure to the virus. They detected antibodies to WNV or a flavivirus (probably WNV based on its presence in the study area) in 12.5% and 12.3% of birds in 2018 and 2019, respectively.
During the two-year study and the analysis of more than 500 samples from Minnesota, scientists found most of the sampled birds hadn’t been infected with WNV. However, 12% of birds had antibodies, indicating these birds had been infected with WNV and survived.
At this time, controlling mosquito populations or trying to vaccinate birds against infection would be expensive, inefficient and ineffective approaches. Therefore, the best way to ensure healthy populations of ruffed grouse persist is by creating high-quality habitat, as noted in the study abstract.
“Management options for mitigating WNV impacts and other stressors consist primarily of providing high-quality Ruffed Grouse habitat that produces birds in good condition that are more likely to recover from infection.”
According to the study, WNV was introduced to North America more than 20 years ago, but scientists are still working to understand its full impact on individual birds and bird populations.
Additional Details About the Study
Dr. Roy said there weren’t any significant spatial clusters of WNV cases in Minnesota, which would indicate hotspots of infection where the virus is more prevalent. The study also found that WNV antibodies were slightly more commonly detected in adult male grouse, although this pattern wasn’t statistically significant. However, because there’s no data to indicate whether males or females are more likely to be exposed to the virus, it could be possible that male birds are better at surviving an infection. This will require additional research to determine.
A similar study in Pennsylvania by Stauffer et al. (2018) showed that grouse in areas with high-quality habitat were less impacted than those in areas of poor quality. Overall, birds in poor condition are more susceptible to a wide range of threats. Minnesota isn’t seeing the same patterns as Pennsylvania, where there’s a significant loss of habitat and a noticeable decline in populations.
In Minnesota, the drumming survey data indicates a healthy breeding population that’s still cycling around a stable long-term average. Minnesota has abundant forests in the northern part of the state, which hosts the highest ruffed grouse numbers.
However, the drumming survey in Minnesota is conducted before nests hatch, so it doesn’t reflect hatching and survival of young over the summer. If WNV reduces survival over the summer, hunters might see fewer birds in the fall than expected based on the drumming survey data alone. However, this mortality might not exceed the levels that would reduce the long-term population trend, much like when hunting mortality isn’t additive to natural mortality.
It was outside the scope of the study to determine the number of birds that may have died from WNV before the fall hunting season. There are still questions about how fatal infections might be for some ruffed grouse over the summer.
The Need for High-Quality Habitat
“We need to manage [forests] for a diversity of age classes to meet the needs of ruffed grouse, as well as other species,” said Dr. Roy. “Grouse have specific needs for each season and they require varying habitat types throughout the year.”
Currently, Minnesota is home to one of the healthiest grouse populations in the U.S., largely because of the abundance of forests on the landscape that contains high-quality habitat. RGS & AWS are working with the Chippewa and Superior National Forests to implement shared stewardship projects to ensure habitat creation.
RGS & AWS are also leading the Moose Habitat Collaborative project, which highlights moose as a charismatic megafauna that relies on healthy forest diversity. In addition to benefiting Moose, habitat creation will help ruffed grouse, American woodcock and a wide range of both game and non-game species. The project, located in Northeast Minnesota and paid for through the Minnesota Outdoor Heritage Fund, is in its fourth phase. When all phases are complete, the total acres impacted will top more than 25,000.
These forest conservation projects are critical to the stability of ruffed grouse populations, especially in the face of threats like WNV.
How You Can Help
Dr. Roy recommends that landowners interested in managing private land for wildlife habitat reach out to the DNR and other natural resource professionals for resources and assistance. Most land in Minnesota is privately owned, and there are many programs available to private landowners to help meet their conservation goals on private land.
Landowner assistance can be provided by RGS, DNR Forest Stewardship, DNR Forest Legacy, Minnesota Forest Association, the American Bird Conservancy, Natural Resources Conservation Service, Soil and Water Conservation Districts and U.S. Fish & Wildlife Service Partners for Fish and Wildlife. More information about these programs and others intended to assist landowners can be found at https://dnr.state.mn.us/privatelandhabitat/forest-habitat.html.
RGS & AWS also encourages all members to participate in the public input process for creating forest habitat. These opportunities are posted publicly through county, state and federal notifications. You may also contact RGS Forest Conservation Directors to learn how to help with forest management on private lands.
While scientists are still unsure how many grouse succumb to WNV over the summer, the research clearly shows that grouse have a fighting chance if we provide them with high-quality forest habitat. As always, we look forward to working with all our chapters and members to achieve that goal.
