West Nile virus again expected to shorten Pennsylvania grouse season
Stevens, Pa. — With West Nile virus on the rampage again this summer, biologist Lisa Williams is not expecting good news when she finishes the most recent ruffed grouse data.
If the news is as bad as the Game Commission’s Pennsylvania Game Commission grouse, woodcock and dove specialist anticipates, it could lead to a recommendation that grouse season be shortened again.
The January 2018 season has already been eliminated due to low grouse numbers.
West Nile virus is a proven killer of ruffed grouse and many other bird species. Research suggests that grouse are particularly susceptible.
The disease can also infect humans – with eight cases recorded in Pennsylvania this year. Williams provided a report to commissioners during their Sept. 25 meeting at the Middle Creek Wildlife Management Area.
“The Pennsylvania Department of Environmental Protection had the earliest detection of West Nile virus ever and positive tests (on mosquitoes and birds) are running at a much higher level than the 10-year average,” Williams said.
She showed the commissioners a graph depicting grouse abundance by year. Unfortunately, there were many more down-slopes than upward ticks on the graph.
“We are at record lows even in our best habitat,” Williams noted. “In the past, each high West Nile virus year has been followed by a drastic drop in grouse numbers. I’m afraid that 2017 will reflect another drop. Most of our neighboring states are also at record or near-record lows.”
This past summer, the Game Commission, state Department of Environmental Protection and Penn State’s Fish and Wildlife Cooperative Unit collaborated to conduct mosquito research at Scotia Barrens, State Game Land 176, in Centre County.
For over a decade, DEP has collected data related to the increase in West Nile virus in the Keystone State, primarily from higher density areas of human population. This has included incidences of bird mortality, mosquito wriggler surveys, and occurrences of humans diagnosed with the virus.
The collaboration aimed to determine how the prevalence of West Nile virus in Scotia Barren’s mosquito wrigglers, collected in grouse habitat, compared to DEP’s data. Researchers selected eight sites on game land 176 for the 10-week study.
“Through the first eight weeks, we collected 13,390 mosquitoes representing 25 different species – and I think that all but about 20 mosquitoes bit us,” Williams said with a smile.
“Eight of the species identified are known to bite birds and to be West Nile virus vectors. Culex restuans was detected at every site. That species was the most common and it is the second biggest vector of West Nile.”
West Nile virus was first detected at Scotia in July, and what we found in the grouse habitat reflected what DEP found elsewhere, Williams pointed out.
“The samples collected during the late summer, weeks nine and 10, have not yet been tested.”
Williams noted that very few mosquitoes were found in the larger functioning wetlands at Scotia. In contrast, smaller puddles were the biggest producers of mosquitoes carrying the virus. Therefore, treatment of those pools might be an option.
“Basically, where you have grouse, you have West Nile virus,” Williams said, while pointing at a color-coded map of the state. She remarked that, in some areas, there seemed to be more grouse that survived the virus.
Based on that analysis, she would like to see a study to determine whether there might be a genetic reason for their survival.
“This is an urgent management situation,” Williams emphasized. “What will happen if we get more bad years in a row? We still have enough birds to work with in the north, where there is better habitat.”
Williams outlined for the commissioners three management options that might be used to maintain sustainable and huntable populations of grouse. One would be to eliminate mosquitoes by directly treating the smaller mosquito-laden pools.
Additional investigation would be needed prior to possible implementation to determine how direct mosquito control might affect other species and its feasibility in a wild setting, she said.
A second option recommended by Williams would be to focus habitat management in areas where the most robust grouse populations still occur.
“I am in discussion with (Game Commission) regions now regarding where we have found West Nile virus-resistant grouse and what management opportunities might be prioritized in those regions,” she said.
According to Williams, habitat management should include the best management practices favoring grouse, as well as focusing on creating brood habitat.
“Habitat management that enhances brood survival may have greater benefit to grouse populations than any other action,” she said. “Where broods have quality habitat, survival rates are higher. Herbaceous groundcover, invertebrates, and high midstory stem density (brambles, shrubs, saplings) are key brood habitat components.”
The third option mentioned by Williams was harvest management. Although she did not dwell on this option at the meeting, she indicated that it was one of the few tools in the “management toolbox” that could be considered.
After the meeting, Williams elaborated on this option and the others.
“I will make a season recommendation to the Board of Commissioners at their January meeting. My recommendation will be based on this past year’s flush rate and summer-sighting data, which is still being received and processed,” she said.
“Basically, anything that I say about a harvest recommendation would be premature at this point. In the meantime, we will continue to focus hard on habitat management.
“We should be prudent and our goal should be focused on getting West Nile virus resistant birds into the breeding population.”