Conclusive Evidence that West Nile and Habitat Loss can Spell Disaster for Ruffed Grouse
Republication with permission, the below article was originally written for the Pennsylvania Game Commission News publication. Written by PA Game Commission ruffed grouse biologist, Lisa Williams, and originally titled, “Ruffed Tumble – Changing Times for Grouse.” The article explores the most current research, understanding and impacts of West Nile Virus and Habitat on Ruffed Grouse in Pennsylvania.
If I had to use one word to describe the grouse situation in Pennsylvania, it would be “change.”
Hunters feel it. Grouse managers feel it. And maybe grouse feel it, in some unknown way.
For hunters, it’s getting harder to find grouse when the season opens, and that season isn’t as long as it used to be. For grouse biologists and foresters, it’s harder to know if a habitat project will attract grouse.
Normally, I don’t like change. I suspect many hunters agree. Maybe that’s why the changes occurring in the grouse populations are especially unwelcome.
But change never stops and neither can we. The Game Commission has been intensively studying grouse declines since 2015. We have learned much and are putting this new knowledge to work as quickly as possible.
Our research has shown two factors are driving grouse declines. The decades-long loss of high-quality young-forest habitat has been impacting grouse severely. And on top of that, West Nile virus has been killing Pennsylvania grouse since the early 2000s.
For nearly a century, Pennsylvania has been losing young forests – the seedling and sapling stands that form our future woodlands. This loss has sobering implications for the quality and quantity of our future forests.
Young forest is lost through the natural process of time and growth. Pennsylvania largely was clear-cut through the late 1800s, with forests regrowing through the 20th century. Today, much of Penn’s Woods is 90 to 120 years old; young forest makes up only about 8 percent of it, a more than 70-year low.
Young forest currently covers only about half the acreage needed by species that rely on this habitat. More than 30 species – from wood turtles to woodrats to whip-poor-wills – suffer from this loss of critical habitat and are now considered species of greatest conservation need.
This loss also has been a primary driver of grouse-population declines. For grouse, there is no substitute for a well-balanced forest made up of multiple age classes.
Grouse use different-aged stands for different reasons in different seasons.
Forest openings with downed logs, brambles and scattered saplings make excellent brood habitat. Dense sapling thickets are used for drumming and courting. Mature forest often is used for winter cover, nesting, and feeding on nuts, twigs, buds and fruit.
Over the past 70 years, the loss of young forest almost has gutted the habitat needed for two of the three critical life requirements for grouse: brood rearing and courting.
In response, populations have steadily declined, shifted northward, and become ever-more restricted to localized areas of suitable habitat.
As good coverts become farther and farther apart, declining populations get no assistance from new birds entering the area. Small populations in isolated habitats are more vulnerable to a variety of threats.
This trend has been occurring for decades, primarily in southern, eastern and western Pennsylvania. But in the early 2000s, such vulnerability rapidly fueled widespread population declines when a new threat entered Pennsylvania.
West Nile virus (WNV) first was found in North America in 1999. It coursed through Pennsylvania from 2001 through 2003, and remains a health threat to humans, domestic animals and wildlife.
While it was evident early on that crows and jays suffered high mortality from WNV, we now know grouse were impacted, too.
And, for grouse, the virus became the straw that broke the camel’s back in many areas of the state.
Many populations that had hung on as they lost habitat, winked out after WNV hit.
Although grouse remain abundant at the state level, predicting where to find them and how they might respond to habitat management has become a guessing game in many areas.
But our ruffed grouse and wildlife health programs have been hustling, on a shoestring budget, to take the guesswork out of grouse management and get managers back into the driver’s seat.
In working with private, state and federal partners to conduct intense research on West Nile virus and investigate other issues that might be involved in grouse declines, we’ve learned a lot.
Here’s a sample:
- Ruffed grouse are highly-susceptible to WNV, and infected grouse suffered very high mortality, based on our 2015 lab study with Colorado State University.
Young forest is important habitat for grouse courting and brood-rearing, but only 8 percent of Penn’s Woods is made up of young forest. Habitat loss and degradation have left grouse populations more vulnerable to threats, including West Nile virus.
We still don’t know how many other woodland birds are vulnerable to the WNV.
- Wild grouse are exposed to WNV throughout Pennsylvania, in good and poor habitat.
We know this from looking for WNV and virus antibodies in hundreds of hunter-harvested grouse from 2015 through 2018. We also see evidence that the proportion of WNV survivors among harvested grouse varies with the virus’ severity in any given year.
There is no way to know how many grouse die during the peak WNV season – July through September, but we see fewer survivors in the fall/winter harvest during severe WNV years.
- Both young forest availability and WNV prevalence determine the fate of grouse populations.
A 2017 Game Commission-Penn State University analysis showed habitat and WNV influence whether grouse persist in an area, whether they colonize new areas, and whether individual populations disappear over time. This gives us something to work with! We now know our management efforts will be more effective if we take disease prevalence into account when managing habitat.
- Individual grouse in areas of highly abundant and high-quality habitat might have a higher chance of survival, based on antibody findings.
Further, hunter-flush-rate data show grouse populations in good habitat rebounding more quickly after bad WNV years, compared to populations in more isolated or marginal habitats. This also has valuable management implications.
- We’re more knowledgeable about the primary disease vectors, based on a 2017-18 collaboration with the state Department of Environmental Protection’s West Nile Virus Surveillance Program.
The mosquito Culex pipiens is the primary WNV vector in human residential areas. But Game Commission trapping shows it’s rarely found in the state’s forests. Rather, the vector we must target is Culex restuans, a closely-related country cousin of Culex pipiens that prefers to target birds.
Our 2017-18 research shows Culex restuans thrives in woodlands, occurring in each of the 10 game lands we’ve studied.
- We know Culex restuans populations rise and fall largely due to temperature and rainfall. WNV transmission benefits from above-average spring and autumn temperatures, because warm temperatures prolong the mosquito-breeding and the WNV-transmission season. Unfortunately, we also know WNV is not going away. High-prevalence years are becoming more frequent. Eight of the past 10 years exhibited extremely high WNV prevalence.
WHAT WE KNOW NOW
As the discoverer of West Nile virus impacts on ruffed grouse, I hear from a lot of frightened grouse hunters and frustrated colleagues.
Once WNV infiltrates grouse populations, the tendency is to give up. I hear it from Pennsylvania hunters and I’ve seen the nothing-we-can-do-now mentality attached to a lot of reports from across the country.
But I reject such statements outright.
I understand the shock people experience as they grapple with the idea of this virus suppressing grouse populations. But the day we give up is the day we lose.
To safeguard grouse, the Game Commission in 2017 shortened grouse season for the first time since 1960.
Closing the post-Christmas season is designed to decrease the removal of birds from the population in mid-winter, and correspondingly increase the number of birds entering the breeding population.
Even though the late season is a favorite among grouse hunters, over 70 percent of the more than 300 season-related written comments received since 2017 supported the closing.
Recognizing grouse-population declines, Pennsylvania’s passionate grouse hunters have been willing to give up days afield to help restore populations.
A structured framework now recommends season length based on grouse population levels. This is a consistent and transparent system that provides a mechanism for the season to lengthen as grouse populations recover. A competing-models analysis will be used to detect any impact of season changes.
Even with all the buzz about mosquitoes, we must remember habitat availability primarily influences whether grouse populations thrive.
High-quality young forest habitat supports the continued existence of grouse populations, as well as their ability to colonize new areas. Where young forest is of high quality and highly abundant, grouse populations are more resilient and can recover from annual losses in bad disease years. But disease impacts are stronger, and recovery is weaker where grouse occur in marginal, isolated habitats.
We must work actively to expand the acreage and connectivity of young forests, while ensuring the habitat we create is strategic and of the highest quality.
With reinforced urgency, the Game Commission is leading the way on grouse-habitat restoration. The agency has increased the acreage of timber harvested on state game lands by 50 percent in recent years. Our foresters also have adopted an intense focus on aspen management, and the agency has hired additional forestry staff, resulting in dramatic increases in non-commercial acres being turned back into young forest.
In addition, the Game Commission is incorporating focused grouse-habitat management into the review process for all game lands comprehensive plans, and has committed significant funds for forest rehabilitation and restoration.
An additional $500,000 has been added to the $750,000 already allocated this fiscal year to support forest-management projects that can’t be accomplished through commercial timber sales.
Now is the time to double-down, triple-down, quadruple-down on habitat.
Land managers have struggled for decades to create enough young forest to maintain healthy grouse populations, let alone recover populations suffering disease losses. So, in addition to making more new forestland, we must put it where it can accomplish the most good.
Young forest created today will take a few years to mature into prime grouse cover. So we need to be sure we’re putting grouse habitat in places where birds quickly can take advantage of it.
In short, we need to figure out where healthy grouse are and where disease isn’t.
Where do strong, huntable grouse populations occur? That’s a population with which to work!
Put enough habitat there for youngsters from that seed population to safely disperse and establish new territories. Make enough so birds can move in and out of areas, so breeders find other breeders, populations find other populations, and gene flow is assured.
By working near areas where grouse already occur, we maximize our effectiveness, because our work will immediately benefit populations facing change.
Meanwhile, we’ll seek to identify where West Nile virus is most abundant and where virus-carrying mosquitoes are located. Are there landscape barriers and thresholds we can work with? What factors limit vector populations? Elevation? Slope? Distance from water? Distance from forest edge?
If we can crack the code on WNV, then we know where to invest in habitat. This has become the focus of Game Commission research.
HOW TO HELP
Whether you own land or not, every Pennsylvanian has a role to play.
Have you heard the public health announcements asking people to remove spare tires, empty planters and other containers holding water around our homes? Empty them!
In the forest, our research indicates that shallow stagnant puddles – equipment ruts, ditches and poorly-drained roadside berms – are our spare tires.
Culex restuans thrives in small water sources that lack natural predators. Removing stagnant mosquito-breeding pools around your home, farm or camp can help reduce the risk to all, including grouse!
Fully functioning wetlands and springtime pools filled with dragonfly larvae, backswimmers, diving beetles, and frog and salamander eggs generally do not pose significant WNV concerns, because they support mosquito predators.
Defining landscape barriers and mosquito-pool characteristics will remain a focus of Game Commission research, so we can continue to provide science-based guidance to public and private landowners.
Finally, we need to recognize we won’t sustain populations on public lands alone – grouse don’t recognize boundaries.
Grouse must get more assistance from private landowners. As hunters, we must educate our families, our neighbors and our fellow hunters on the importance of creating young forest on their lands. There are Game Commission biologists and Department of Conservation and Natural Resources foresters who can advise landowners on how to create young forests sustainably and responsibly.
If there’s one silver lining in the WNV dark cloud, it’s knowing that a disease impacting Pennsylvania’s state bird has added a renewed sense of urgency to our call to restore young-forest habitats.
New partners are getting involved constantly, and many determined hands are creating high-quality grouse habitat.
Habitat + Research + Education + Harvest Management: That’s how we’re going to adapt to the changing world ruffed grouse now occupy. That’s how we’re going to tip the odds back in favor of the King of Thunder and other vulnerable woodland species.
Now is not the time to give up. Now is the time to get busy. Change never stops, and neither will we.