Pennsylvania’s state bird is in serious trouble. The ruffed grouse, known for its signature wing drumming in the spring woods, and speedy, explosive flushes when startled, has been vanishing from the landscape.
After reaching a population apex in the mid 1990s, the non-migratory bird that has little problem surviving the harshest of winters has fallen victim to the repercussions of human interaction.
For the past five years, Pennsylvania Game Commission Grouse Biologist Lisa Williams has been intensively studying grouse population decline, and is working to stop the trend.
“For grouse, you have two factors,” Williams said. “One kills you slow and one kills you quick. The one that kills you slow is long-term habitat loss; they’ve been losing habitat for decades.”
A newer threat – “The one that kills you quickly,” Williams said – is West Nile virus. Traced to accidental importation of foreign mosquitoes hitching rides on cargo ships from Africa, western Asia, and the Middle East, to New York City in 1999, the virus has spread across the North American continent. Birds and mammals bitten by the foreign mosquito were subsequently bitten by native mosquitoes, which then spread the virus.
“Now it’s a common disease which we will never get rid of, because it’s in our native birds and it’s in our native mosquitoes,” Williams said. “It’s here to stay.”
Factor 1: West Nile virus The Centers for Disease Control and Prevention has named 300 different bird species that have tested positive for West Nile virus, led by crows and jays.
“We now know that that virus is very deadly to grouse,” Williams said.
Mosquitoes bite the fleshy rings that surround birds’ eyes, or between the scales of their legs. Chicks with under-developed feathers are highly vulnerable to the infected insects, she said.
Grouse populations that have been clinging on in areas of bad habitat – the southern two-thirds of Pennsylvania, Williams said – are taking the brunt of the virus. In the northern tier counties where habitat is better, she said, “they can almost keep up with the disease; they can get ahead of it.”
Williams said different bird species have responded in different ways, with varying levels of mortality. Some die quickly, while others become sick, but survive. Some don’t seem to get sick at all. “It almost sounds like COVID in some ways,” she said.
Following a hunch that the virus was affecting grouse, Williams conducted a study in 2015 with Colorado State University.
“We found that 40% of the grouse chicks that we gave the virus to died very quickly,” she said. “The chicks died within two weeks. The other 60% of the sample looked OK.”
But she said that after two weeks, they developed heart and brain damage so badly that they would not have survived in the wild. “That was sort of an ‘Oh brother!’ moment.”
She said: “We know some birds can get it and survive in the wild, and they recover. Theoretically they should be immune, as they’ve acquired the antibodies. What we’re finding, though, is that it seems that they’re not surviving more than a couple of years.”
Healthy grouse can live as long as 10-11 years in captivity, but a West Nile infection drops that expectancy to just two.
Another factor is the decline in bat populations, as bats eat lots of mosquitoes. After 20 years of bat population gains, and advances in research, White Nose Syndrome suddenly swept through the U.S. starting around 2008, severely curtailing the bat population.
Factor 2: Loss of habitiat Williams said Pennsylvania has reached a 75-year low for necessary grouse habitat —that is, a young, healthy-growing, thick forest of downed logs, brambles and scattered saplings.
“The stuff that you would have to fight your way through,” she said, “they need that around to protect them from predators.”
Humans “like a forest that looks kind of like a park,” she said. “Wildlife really want a mess. It’s what’s best for them.”
The state was largely clear-cut through the late 1800s, with forests regrowing during the 20th century. Today, much of Pennsylvania’s forest area is 90 to 120 years old. Only 7% is made up of young forest that grouse need for courting, nesting and brood-rearing. “We really need twice that for grouse to really thrive,” Williams said.
So how were grouse able to survive in forests of virgin timber before humans arrived? Williams credited beavers, which create swamps by cutting down small trees and damming streams. That process allows witch hazel and berry thickets to take root and create quintessential grouse habitat, the biologist said.
Unregulated trapping dramatically changed the state ecology. “Exporting beaver pelts was a huge industry,” Williams said. “It had a profound effect.”
Tree loss due to disease and blight is nature’s way of killing off certain species and leaving voids in the mature forest, along with wind storms, which opened small pockets of grouse habitat.
“The other thing that really changed was the role of fire,” Williams said.
John Rucosky is a photographer for The Tribune-Democrat. He can be reached at 814-532-5055. Follow him on Twitter @JohnRucosky.