West Nile does have a particularly serious impact on corvids. However, what happens over time is that birds that have been exposed and survive produce successive generations with greater resistance to the disease. So while WNV may be a short term problem for grouse, it's less likely to be a long term problem. Which is at least some good news for those of us who might have to suffer through a few seasons' worth of reduced numbers. The bad part for the near term is that it's happening when we should be looking at the next peak in grouse numbers.