What significant impact does West Nile virus have on birds?

West Nile virus has a significant impact on bird populations, primarily characterized by high mortality rates. Birds, particularly certain species like American crows, jays, and magpies, are highly susceptible to the virus. When infected, these birds often experience severe neurological disease, which can lead to death. The virus can spread rapidly among bird populations, affecting the structure and dynamics of avian communities.

While it is true that some birds may experience low infection rates or show no effects, the overall impact of West Nile virus is most substantially felt through the high mortality it causes in highly susceptible species. This high mortality can disrupt breeding populations and ultimately affect biodiversity and ecosystem health. This underscores the virus's role as a significant factor in bird population dynamics rather than causing a mere decrease in lifespan or having no effect at all.