Abstract
In the winter of 2006, a mass mortality of Tree Sparrows Passer montanus was reported in central Hokkaido, mostly from citizens with bird feeders. We compared the seasonal change in sparrow density, from route-census surveys on the Hokkaido University Campus, during a normal period (2003-2004), and during the period which included the mass mortality event (2005-2006), in order to evaluate the density change in the sparrow population in Sapporo. The fluctuation of sparrow density in the 2003-2004 period was small. However, a sharp drop in density was documented between December 2005 and January 2006. The timing of the population crash synchronized with the start of citizens' inquiries. It suggests the importance of the citizen's role as population monitor of common birds such as Tree Sparrows. Since Japan lacks an emergency response system for a wildlife crisis, it is essential that a nation-wide monitoring system of wildlife health be established, and people in the related fields (e.g. government officials, NGO's, and research scientists) share information to maximize observations from citizens recognizing an ecosystem crisis.
