An update on West Nile Virus in Ruffed Grouse and a test kit how-to video.
The second-year results for the Great Lake states’ collaborative West Nile Virus (WNV) study are in, and there’s good news, bad news and hope, for ruffed grouse in Michigan, Wisconsin and Minnesota.
In total, hunters provided 786 samples in all three states from the 2019 hunting season: 281 from Michigan, 188 from Wisconsin and 317 from Minnesota. The total number of samples was up a bit from the 721 submitted the year prior, though Wisconsin’s individual sample total went down. In 2018, Michigan tested 213 samples, Wisconsin tested 235, and Minnesota tested 273. While some birds did test positive for WNV antibodies, the percentages were low. The results from 2018 and 2019 also showed that these birds can survive being infected.
Michigan’s tests from the 2019 samples are still being checked in the lab, but Michigan Department of Natural Resources Upland Game Bird Specialist Al Stewart says the other states saw no major changes compared to their 2018 results, and he expects the same for Michigan.
“In 2018, 13% were positive for antibodies consistent with West Nile exposure. There were nine, or 4%, that was confirmed for West Nile Virus exposure, and there were 19, or 9%, that was likely exposed to West Nile Virus. Then there were four, less than 2%, positive for the virus [at the time of harvesting],” noted Stewart.
Minnesota’s positive rates have been similar to Michigan, with 12.3% (39 birds) testing positive in 2019. This was right on the mark from the first-year of 12.5%. No birds sampled in either 2018 or 2019 had the virus in its heart when harvested.
Wisconsin had a higher rate of positive tests. Of the state’s 188 samples, 20% (37) tested positive, compared to 29% from 2018. Like Minnesota, Wisconsin had no grouse with the virus in the heart among their 2019 samples, though two birds tested positive for the virus in the heart tissue the prior year.
It should be noted that officials testing birds split positive cases between “confirmed” and “likely.” All three states had more likely cases than confirmed, it was most notable in Minnesota where 36 of the 39 birds were labeled as likely infected. Further, 20 of the 37 birds in Wisconsin and 13 of the 20 birds in Michigan were likely to have been exposed. But Charlotte Roy, grouse project leader with the Minnesota Department of Natural Resources, notes that this doesn’t mean a likely case is not West Nile Virus in ruffed grouse. Rather, it’s a detection that the bird was exposed to a flavivirus, and because WNV is the only flavivirus known to have an impact on grouse in that area, it can be reasonably assumed the bird indeed contracted WNV.
“When they do these tests, they are basically looking for antibodies that are either West Nile Virus confirmed or flavivirus confirmed,” Roy said. “There are a lot of flaviviruses, and because West Nile Virus is known to occur in this region, it’s likely it was West Nile Virus. When they do these tests, they’re looking for a certain signal strength. If the signal strength is very strong that’s a West Nile Virus positive, but if a signal strength is not as strong, then they call that a positive for a flavivirus.”
While these tests show that birds can recover, there still is a gap in the information provided. Because tests are submitted from harvested birds, these states aren’t getting a look at the immediate impacts of WNV. The Minnesota DNR makes this clear in documents sent out to hunter cooperators, stating that the study doesn’t inform biologists how many birds are killed by the virus when it emerges over the summer before these samples are collected during the following hunting season. Roy expanded upon this, noting that even though some birds are being lost over the summer from the virus it’s still great to see grouse do survive exposure to WNV.
“That we had no virus in the hearts was a good sign,” she said. “There is the possibility that some of them may have died and were not available for sampling in the fall. We really don’t know for sure how many birds might have had each of those outcomes, but we do think that some of the exposed birds are surviving and aren’t sick when they’re harvested in the fall.”
When it comes to Wisconsin’s testing, it’s worth asking if the smaller number of hunter samples – whether due to turnout or the way the DNR distributed tests – affected the results in some way, namely raising the positive percentage. Wisconsin DNR Assistant Upland Ecologist Alaina Gerrits said that this is a possibility, but there are so many variables between the three states that it likely isn’t a huge impact.
“It’s honestly hard to say,” she said. “Last year we had a few more samples – I think we had about 230 – and we had similar percentages. There’s a lot of different variables: Different mosquito populations levels in Wisconsin versus Michigan or Minnesota, there could be different weather patterns that contribute to that, it could be a sample size issue, so honestly, it’s hard to say.”
Plus, 20% isn’t a number worth raising alarm about, Gerrits said, because it’s showing the birds are contracting the disease – something previously known – and that they’re recovering. She said it’s not much different than humans contracting the flu, creating antibodies and recovering.
Speaking of infectious diseases in humans, another issue with testing has arisen due to the COVID-19 pandemic. Because passing out testing kits to hunters goes against current health and safety guidelines, the Michigan and Wisconsin DNRs won’t be able to send out new tests. Minnesota doesn’t have to worry about this since its two-year study is now over, but this means hunters are going to have to use previously-received tests in the other two states. This may cause a decrease in birds tested, but it will still help to have some data. Luckily, nothing in the tests expires, so they’re still as good as new.
We know that West Nile Virus has been affecting grouse populations in the lower-48 states since it was first detected in North America in New York State in 1999. Looking beyond the Great Lakes region, Pennsylvania is a state that has seen significant decreases in grouse abundance over the 20 years that WNV has been present. Prior efforts to assess the effect of WNV on ruffed grouse populations in the state emphasized the importance of high-quality young forest habitat at a landscape scale. Individual ruffed grouse have a higher rate of survival – and populations appear to recover faster and seem more likely to persist – in regions of the state with higher quality, more abundant habitat. Though Pennsylvania has picked up on a pattern seeming to connect WNV impacts to habitat conditions, the Great Lakes states in this study have an abundance of proactively managed multi-stage habitat in much of their grouse range, and are not experiencing nearly the same level of WNV impacts. This may provide further indication to biologists and foresters in other states that, even with the initial impacts WNV has on birds, proper forest management gives them a chance to shed the disease and live.
But this is still just an educated guess based on little data. Gerrits specifically said that in Wisconsin, they can’t draw a conclusion or make a correlation between the level of habitat that’s available and the amount of WNV spreading across the landscape. And, because science is based on hard data from studies, right now Gerrits said she can only say, “The more quality and higher quantity of good habitat that there is, the more suited grouse are going to be able to overcome any stressor whether it’s weather, predation or diseases.”
Even pristine habitat can’t protect every bird, though. Take the Summer rains in Michigan for example. It’s likely that due to these heavy rains which caused dams to break in Sanford and flooding to mix with Dow Chemical containment ponds in Midland, habitat in those areas of the state and others seriously damaged will not hold many birds. But, if there is pristine habitat, birds will still return to it and start their cycle over again.
“Michigan is really focused, and always has been, on maintaining young forest habitat,” Stewart said. “That’s what we’ll continue to focus on. Because of that, these variations like disease or bad weather that can affect population, our goal is to make sure grouse don’t get stressed. Like anything else, some critter that’s stressed is more susceptible to disease or other harsh conditions. With grouse, we’re trying to provide that best habitat [so] if something occurs they’re resilient enough to come back and expand from there.”
The Wisconsin DNR is taking an innovative approach when tackling their habitat problems. It maintains partnerships, such as a young forest habitat partnership with the Ruffed Grouse Society, where RGS works with private landowners to create timber management plans on small tracts of land. For example, in the southwest part of the state, in the driftless region, bird hunting was phenomenal in the 1980s and 90s. However, in the last two decades, there has been zero detection in drumming surveys there. Why?
The loss of the timber industry.
Further, the land was parceled off in small segments, 40-80-100 acres, and landowners tend to be more hesitant to manage it – “Because of stigma with timbering, or they think it will disturb wildlife,” Gerrits said.
“Engaging private landowners is a really important thing in creating young forest habitat,” she added. “Our county forests do a good job, our state lands do a great job, the national forest in the northern half of the state – they have a few more hoops to jump through to harvest timber but have an active timber industry and it is very important.”
Brent Rudolph, Chief Conservation and Legislative Officer with the Ruffed Grouse Society and American Woodcock Society, also notes that connectivity of habitat is an important factor aiding grouse resilience or recovery from WNV impacts.
“Connectivity is different from the basic consideration of quantity of habitat,” he said, “and will be especially important for grouse on the edge of their distribution.”
Rudolph explained that even where relatively abundant, high-quality forest habitat is available that could support decent local numbers of grouse, a spike in WNV mortality in a particular year – or even worse, over a few years strung closely together – could deplete those grouse numbers if there are no other nearby sources of new broods and dispersing birds to overcome those losses.
“Ruffed grouse are not a long-lived species,” Rudolph said. “They can ordinarily tolerate booms and busts and persist over the long-term, but if West Nile Virus in ruffed grouse is adding a whole new source of mortality to scattered populations, grouse may struggle to persist even in habitat that looks ideal for them. We need to guard against this so that the future of grouse conservation will not depend entirely upon scattered strongholds in increasingly shrinking and isolated areas.”
Finally, Minnesota’s study is over. With funding for just two years and now with funds dwindling even more because of the COVID-19 pandemic, Roy noted that she’s not sure what the future holds in terms of expanding upon this two-year project. She and her colleagues do know, however, that habitat is key and they’ll continue to provide that for the birds. The DNR is also in its second year of a brood survey that Roy hopes gives some answers about what’s happening over the summers.
“At present, it’s not feasible to reduce mosquito populations at the scale that would be necessary to have an impact,” she said. “We’re not going to attempt to vaccinate birds or anything along those lines so it’s important that the key message is, by providing good habitat for birds, you’re producing birds that are stronger and have better immune responses that will better equip them to recover from infection. I want that to be something that people realize. One thing Minnesota is currently attempting to do is try to get a sense of how brood production is varying from year to year, so we just launched a new brood survey that’s being done each summer to get a sense of that. We’re in the second year of doing that and we hope that we’ll have a better sense of how the production of broods may vary from year to year with that data. It won’t give us any causes of mortality but it will hopefully give us information about the production of broods on the whole.”
Through all of this, the biggest take away is that overall there is an opportunity for a bright future. While things will vary state-to-state and this data really only applies to the core area the bird was taken from, it does give hope to other states on where to start – making sure early successional habitat is present and created on a regular basis. It also has helped Wisconsin find new avenues to help their birds, and will likely help others, too.
“The study was initiated to dip our toes in the water, to look at the prevalence [and] distribution of the disease. It was something we’ve never sampled for and we didn’t have this awareness of what level this disease was occurring in our population,” Gerrits said. “I’d say the bigger goal and picture for us, is that we just rolled out a new ruffed grouse management plan last year and this is one of the components within the plan, but for us the big goal is habitat. [In addition to] working with private landowners, [we’re working with] other partners like the County Forest Association to cut timber and help foster a hunting community, working on a citizen-science app to get people activated and engaged where people can track broods, increase awareness, and reverse the stigma of timber harvests.”
The coordinated effort to monitor WNV in the Great Lakes sets a good example for the coordination needed to endure any impacts of the disease among other stressors on grouse populations. Engaging multiple partners and working across different landowners to improve awareness and increase management efforts can allow grouse to persist and even expand back out from their population strongholds. West Nile Virus in ruffed grouse shouldn’t be expected to go away, but perhaps in some ways concerns over the threat it poses can help unify such collaboration, and ultimately motivate better efforts to secure a bright future for grouse.
Test Kit Unboxing and How-To Sample for West Nile Virus in Ruffed Grouse.
While Covid-19 prevented new tests kits to be distributed in 2020, a significant number of WNV test kits remain in the hands of grouse hunters in Michigan and Wisconsin. Anyone with an unused test kit in those states is encouraged to collect samples and submit them this fall.
***For COMPLETE instructions and more information on disease sampling in Wisconsin, please visit the WI DNR website: https://dnr.wisconsin.gov/topic/hunt/ruffedgrouse.html