The collapse of the greater prairie chicken population in Jasper County was mirrored in reduced hatching rate of eggs.

 EXPERIMENT   In 1992, researchers began experimental translocations of prairie chickens from other states to increase genetic variation.

 RESULTS   After translocations, the hatching rate rapidly improved, and the population rebounded.

 CONCLUSION   Lack of genetic variation had started the Illinois prairie chickens down the extinction vortex.