Shiawassee Refuge is a natural laboratory for this study.  Waterfowl and shorebirds are considered the principal biotic reservoirs for avian influenza virus.  The refuge is one of the most important stopover sites for these birds in Michigan.  In fact, the refuge provides habitat for up to 40,000 ducks and 25,000 geese during spring and fall migration.  The virulent H5N1 strain of the virus has not appeared in North America yet.  However, the Mississippi and Atlantic Flyways could be important routes for the spread of the virus.  Further, Shiawassee Refuge sits on the edge between these Flyways.