Quality Habitat May Lessen West Nile Virus Effects in PA Ruffed Grouse

By the Ruffed Grouse Society and Pennsylvania Game Commission

Recent research into West Nile virus in Pennsylvania's ruffed grouse suggests a strong need for landscape-scale creation of young forest habitat to help this popular gamebird thrive.

Research conducted by the Pennsylvania Game Commission, and supported in part by the Ruffed Grouse Society, has begun revealing the effects of West Nile virus on the state's ruffed grouse population, as well as the benefits of having an ample amount of the high-quality young forest habitat that these birds require. (Both the Pennsylvania Game Commission and the Ruffed Grouse Society are partners in the Young Forest Project.)

Ruffed grouse

Research suggests that abundant good-quality young forest habitat may help ruffed grouse overcome the effects of West Nile virus./RGS

The ruffed grouse is designated the state bird for Pennsylvania. The fear that West Nile was affecting grouse populations in the Keystone State emerged in the early 2000s, following reports from veteran upland bird hunters that grouse populations had fallen dramatically and inexplicably.

Game Commission biologist Lisa Williams, in an article entitled "What's Wrong With Our Ruffed Grouse?," published September 2016 in Pennsylvania Game News magazine (see attached file below), notes that "Each year hundreds of cooperating grouse hunters keep diaries for the Game Commission, recording from each hunt the date, county, hours hunted, and grouse flushed and bagged."

Williams's first step in studying West Nile in Pennsylvania grouse was to look closely at "changes in cooperator flushes per hour." The data showed that grouse populations had suffered a steep decline in the early 2000s. While grouse populations are known for having cyclical ups and downs, the data showed that no population boom had followed the dramatic downward trend in Pennsylvania.

West Nile virus was first reported in Pennsylvania in 2000, and by 2002 it had been found in every county. Transmitted by mosquitoes, the virus can be fatal to humans, and it caused large-scale mortality in crows and blue jays in the early 2000s.

The Game Commission began research in 2014 to better understand the impact of West Nile virus on ruffed grouse. Key to the effort was an experimental infection trial on grouse chicks hatched from eggs collected in the wild.

To find grouse nests and eggs, Williams drafted "Grouse Nests Wanted" posters and sent them to organizations whose members would be active in the springtime woods – the Ruffed Grouse Society, National Wild Turkey Federation, Trout Unlimited, Pennsylvania Audubon, mushroom clubs, hiking clubs and local birding clubs. Searchers also included foresters with the Pennsylvania Department of Conservation and Natural Resources, as well as Game Commission biologists, foresters, conservation officers and Food and Cover Corps personnel.

Six nests were found, and some 40 eggs were collected. Housed in a portable incubator, the eggs were driven cross-country from Pennsylvania to a private grouse propagation facility, Grouse Park Waterfowl, in Idaho. There the eggs were hatched and the resulting chicks raised for six weeks.

The chicks were then driven to Colorado State University and housed in a laboratory with a high level of biosecurity clearance. Under controlled conditions, scientists inoculated some of the chicks with the West Nile virus.

Writes Williams, "In all, 18 chicks were involved in the WNV-challenge study: 10 were inoculated with WNV; five were given a WNV vaccine and then inoculated with WNV to see if the vaccine worked; three were housed with the others as a contact-control group to see if the virus would pass directly from bird-to-bird without the presence of mosquitoes."

Ruffed grouse on nest

Volunteers searched Pennsylvania habitat to find nests and eggs of ruffed grouse for West Nile virus study./C. Fergus

Lab workers drew blood from the chicks daily to look for West Nile virus and examine levels of virus antibodies. During the study, none of the vaccinated birds and none of the contact-control birds sickened. However, within eight days, four of the 10 unvaccinated birds inoculated with the virus had become extremely ill.

Later, all birds in the study were autopsied to gauge the effects of West Nile virus. Those effects included "severe lesions that damaged their hearts, brains and other vital organs," wrote Williams. "In total, eight of the 10 [unvaccinated] birds had organ damage severe enough to make their long-term survival in the wild uncertain."

In 2015-16, cooperating Pennsylvania grouse hunters used filter-paper strips to collect blood from grouse they had harvested in the wild. Those samples revealed that 13 percent of the harvested grouse were positive for West Nile virus antibodies, and that wild grouse have been exposed to West Nile in every region of the state.

The researchers believe that West Nile virus does not apply steady annual pressure on ruffed grouse populations, and that the risk to grouse numbers rises and falls over time, perhaps triggered by weather conditions year-to-year.

During the 2016-17 grouse hunting season, the researchers will repeat blood sampling from hunter-harvested birds to increase the sample size and improve and expand their data. Writes Williams, "We will also work with population modelers to shed more light on WNV's impact on grouse populations."

So far, the research suggests that regions with high-quality, abundant young forest habitat show a stronger grouse population recovery between peak West Nile virus periods, compared to regions with lower-quality, less abundant and more-fragmented habitat. Also, individual birds in high-quality habitat regions seem to have a higher survival rate after contracting West Nile, compared to birds in areas with lower-quality habitat.

Concludes Williams, "Lack of a population recovery in four of six [Pennsylvania] regions is likely due to limited young forest habitat" in those four regions. She adds: "Creating abundant, high-quality habitat is the most important safeguard we can provide to our state bird."

The Ruffed Grouse Society and other conservationists view the recent West Nile research results as a call to action to create more high-quality habitat on a landscape scale throughout the range of the ruffed grouse. Williams notes that West Nile virus "had spread throughout the United States by 2005, so this virus might be an unrecognized factor in grouse declines in other states."

According to the Ruffed Grouse Society, young forest habitat creation and restoration is extremely important, owing to the onset of West Nile virus as an additional stressor on ruffed grouse populations. RGS suggests that land managers focus on creating areas with diverse native food sources and thick protective cover to promote the ruffed grouse's longterm health and welfare.