The bacterium Yersinia pestis that is responsible for potentially severe infections sometimes referred to as the Black Death and responsible for the elimination of a large percentage of the population in Europe during the Middle Ages still exists in endemic areas such as prairie dog towns out west. In its natural (sylvatic) cycle, the bacterium is maintained in flea vectors and small rodents. The bacterium is often associated with prairie dog towns where transmission of the bacterium to prairie dogs by fleas results in amplification and further spread of the bacterium. The result is often death of prairie dogs which leads to infection of predator species such as the black-footed ferret. In addition with loss of the prairie dog, decline in both the ferret and prairie nesting birds such as the Mountain Plover and Meadowlarks often occur. Mountain plovers prefer dry habitat with short grass and bare ground for nesting. Loss of prairie dog colonies leads to a decline in nesting habitat for these birds.