As if mosquitoes weren’t aggravating enough. Now it seems they might be playing a role — potentially a large one — in the decline of ruffed groused across Pennsylvania.
The birds are scarce, without a doubt. Population monitoring suggests their numbers hit a 50-year low in 2014, said Lisa Williams, grouse biologist for the Pennsylvania Game Commission.
Hunters can attest. According to Williams, flush rates — defined as the number of grouse flushed per hour by hunters who volunteer to log their experiences — have been almost universally terrible of late.
Statistics from 2014 — the most recent available — show flush rates were down anywhere from 13 percent to 66 percent across five of the state’s six regions. What’s more, 75 percent of Pennsylvania’s 51,000 grouse hunters ended the year without killing one, Williams said.
Just catching sight of one was tough. On average, it took a hunter five more hours to jump a grouse in 2014 than it did in 2000.
“The trend is fairly bleak over the long term,” Williams said.
For years, troubles with grouse were blamed on the aging of state forests. Grouse need early successional habitat — young forests — to survive.
That cover is in short supply, Williams said. But population declines were slow until 2002, when there was a sharp dip, Williams said. A bit of a weak recovery followed, then another precipitous fall.
“So whatever happened happened very quickly, over just two or three years. And it happened all across the state,” Williams said.
Habitat doesn’t change that fast, so this had the “fingerprints of disease” all over it, she said.
West Nile showed up in New York City in 1999, then went “haywire” in 2002, right when grouse numbers fell, “so the timing fits,” Williams said. Ever since, she added, grouse populations and West Nile have fluctuated in inverse proportion. When one’s up, the other’s down.
“We had the smoking gun, but nobody heard the bang,” she said.
To test that theory, last spring the commission collected grouse eggs from the wild on game lands and got them to a USDA-certified, mosquito-free propagator in Idaho. The hatched chicks went to a university laboratory in Colorado.
Ten of 18 birds were infected with West Nile, said Justin Brown, the commission’s wildlife veterinarian. Of the remaining eight, five were vaccinated, and three were given a “sham” infection.
The vaccinated and sham birds survived. Four of the infected birds became so sick they had to be euthanized within a week, and four others were so significantly impacted they would have had a hard time surviving in the wild, Brown said.
“Basically, their hearts were just annihilated with this virus,” he said.
If things continue, the day might come when the commission has to consider changes to grouse hunting, Williams said. But she’s not ready to go there yet.
For now, she said, the task is to figure out where West Nile is and isn’t having an impact and do habitat work “where grouse have the greatest chance for survival.”
“We’ll be looking at this hard over the next 12 months,” she said.