A large portion of the range of the greater prairie-chicken in Nebraska sits squarely on the Sandhills region because of the landscape of unfragmented grasslands. The Nebraska Game and Parks Commission has monitored prairie-chicken populations every year since 1955, and numbers fluctuate from year to year. Greater prairie-chicken numbers in Nebraska grew substantially during the 1980s. What factors are responsible for the population size of prairie-chickens each year? Although mortality from hunters has potential to affect the population, the number of grouse hunters in Nebraska has fallen substantially, and hunting mortality appears to be a non-issue. Other predators, such as raptors, coyotes, and bull snakes remove eggs, chicks, juveniles, and adults from the population. Severe winters, especially cold periods without the deeper snow that the birds use for thermal cover, most likely cause higher mortality of prairie-chickens. Cornfields are used as winter food by prairie-chickens on the edges of the Sandhills region, but the large-scale and long-term conversion of grasslands to croplands substantially reduces habitat. Whereas higher levels of rainfall and soil moisture provide for increased vegetation biomass and insect populations for feeding chicks, droughts reduce levels of cover needed to protect nests from predators and to provide habitat for insects.
Grazing is a complicated factor for prairie-chicken populations. Given what we know about the need for patchiness of habitat, some level of grazing is beneficial. Spring mating areas (lek sites or booming grounds) are typically found in closely grazed or trampled sites, such as those near water tanks. Recent research has found that population growth of prairie-chickens in Nebraska was lowest at moderate stocking rates. A positive response of prairie-chickens to higher stocking rates that have been used since the 1980s may be coincidental with implementation of rotational grazing systems that allow pastures periodic rest and regrowth of cover for prairie-chickens while cattle efficiently utilize an adjoining pasture. The relationship between grazing and prairie-chickens will continue to be a focus of research in the future, and this factor is representative of the complicated, interwoven nature of the landscape and environmental factors that constantly push and pull at prairie-chicken populations.