West Nile virus not thought to hinder Wisconsin ruffed grouse numbers

West Nile virus could be one reason hunters flushed, saw and killed fewer birds this past season, but biologists say a number of factors could have played a role – including heavy June rains during the brood season. (Photo by Jerry Davis)

Wisconsin sportsmen are usually responsible and conscientious in reporting problems they encounter in nature. In addition, they generally respond to surveys when asked.

When called upon, they mail in woodcock wings and leg band information from ducks and bats.

After this fall, the state may be asking hunters and hikers to report ruffed grouse found dead or those acting unnaturally in northern Wisconsin forests.

Something apparently happened to the grouse populations in 2017. While spring drumming counts and early brood surveys were cause for excitement and optimism, come hunting season, the reverse seemed to be poking up an ugly head.

Grouse hunters were seeing fewer birds, and now, in retrospect, came an occasional report from hunters of birds acting “ tame,” or reports of hunters finding more feather piles than usual while in the woods.

Michigan, which does not do spring drumming counts, did some survey work on West Nile virus (WNV) in its grouse population and now suspects some of the grouse were knocked down due to WNV, a mosquito-transmitted disease. The mosquito, which may carry a virus, moves the disease from bird to bird.

The virus has been found in all lower 48 states and many Wisconsin counties. Once documented in a county, Wisconsin no longer tests birds routinely in that county. West Nile virus can lead to bird deaths. Crows and blue jays are particularly susceptible to the virus.

WNV has been known to exist in Wisconsin for about 16 years, but has never been found in ruffed grouse here, although testing has not been extensive. The state tested eight grouse about 10 years ago and all were negative.

While there is very little that can be done if WNV is present, it would be helpful to know the causes in sudden drops in bird numbers. Earlier, wet June weather was suspected to be the main culprit (kills chicks), and soggy spring conditions usually mean more mosquitoes, so the rain could have had a duo influence in causing wet, chilly conditions for young chicks and later optimal conditions for the mosquito vector.

The point is, if the DNR asks for dead grouse to be tested for WNV next fall or if it wants reports of feather piles, tame birds, and abnormal activities, help them out here and elsewhere.

Scott Walter, Ruffed Grouse Society Midwest region biologist based in Wisconsin, is not describing this year’s low numbers as a doomsday, but the more information the better to understand the situation.

It is uncertain what the immediate populations might look like given that the natural bird cycle was on the upswing.

The message Walter wants to leave with hunters is that the DNR, biologists, and health professionals do know about the possibility of WNV in Wisconsin, but they do not – at this point – believe that WNV will limit the population of ruffed grouse.

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