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When and where did prairie chickens come to use (rely on?) agricultural crops in the winter? Hamerstrom et al. (1941) felt that it is extremely unlikely that they evolved with the development of primitive agriculture but adapted to it when it became available and, by altering their feeding habits, were able to greatly extend their range far north of the original limits. It is instructive to consider the winter foods of prairie chickens in Missouri, perhaps the approximate center of their original range. Korschgen (1962) analyzed an average of 420 droppings per month from 8 counties throughout the western range and Toney (1980) studied 281 droppings collected near the 1680-acre Taberville Prairie Refuge (Table 4).

Does use indicate need?

Kirsch (1974) argued that winter food is not a priority for prairie chickens in that they have been documented to utilize buds and will move to winter food sources. Hamerstrom et al. (1941) demonstrated that prairie chickens cannot live on buds alone and Burger (1988) related increased mortality with increased movements. Even if prairie chickens could survive at minimal population levels in the North without agricultural winter foods, it would seem prudent to minimize as many of the environmental stresses as possible for a population that is in jeopardy, such as prairie chickens on the SNG.

Kobriger (1965:789) noted, "Prairie chicken populations shrank as corn acreages decreased, and today the eastern and southern sandhill borders, with both grasslands and corn, support the best prairie chicken populations in Nebraska." Schmidt (1936:200) also speaks of the importance of corn, "Increase in prairie chicken population and an extension of range resulted from the extensive growing of corn by the early settlers." Manske (1987) closely followed the winter habitat use of prairie grouse at the SNG and noted heavy use of corn and sunflower fields and waste grain spilled along the railroad tracks bisecting the SNG. He noted as others have that prairie chickens will pick grain out of cow manure in the winter. He believed that high energy winter food is the primary limiting factor for prairie grouse on the SNG. Rumble et al. (1988) found agricultural crops (corn, sunflowers, and soybeans) made up 72.0, 61.3, and 65.2 (mean x = 65.2%) percent composition of the diet of SNG prairie chickens in the months of December, January and February. In comparison, shrubs made up 0.2, 0.9, and 2.7% (mean x = 1.3%) of the winter diet. Toepfer and Eng (1988) collected 3,945 winter locations from radio-tagged prairie chickens on the SNG and found agriculture types used in 41% of the locations and 70.8% of these were "picked corn."

Food and movements

Toepfer and co-workers (Rosenquist and Toepfer 1995) have continued their studies in northwest Minnesota into what has become the most comprehensive study ever on the winter ecology of the greater prairie chicken. From 1992-1996 they monitored 224 radio-tagged prairie chickens and determined food accessibility was a major factor influencing winter movements. Movements of females from nesting to wintering areas of over 16 km (10 miles) were common while males generally remained with 4 miles (6.4 km) of their booming grounds. Small grains and sunflowers were preferred but standing corn was used when other foods were covered.

Leopold (1931) presented historical accounts which relate migration movements of prairie chickens to winter food supplies. The evidence suggests that mainly females migrated to the south to presumably locate food resources not covered with snow. As corn became a common crop in the more northern areas, prairie chickens became a year-round resident. If, in fact, females did move farther south for better winter food resources, why only them and not the males? The expenses of long movements should have been compensated by some advantage. By availing themselves of better food resources, females could experience enhanced reproductive success the following spring and thus pass on the genetic basis for this behavior. At present, females have larger seasonal ranges than males and move over twice as far in the winter as males which tend to stay closer to their "home" booming grounds (Rosenquist and Toepfer 1995).

Church et al. (1989) determined the combustible energy, gross energy, utilization efficiency, assimilated energy, and metabolizable energy from seeds reported to be eaten in the winter by greater prairie chickens and ranked them as follows:

Excellent -- millet, soybeans
Good -- sunflowers, lespedeza
Fair -- wheat, corn, sorghum
Poor -- buckbrush, pigweed, switchgrass

Summary

1. Agricultural crops are apparently essential for optimum winter survival of prairie chickens in the fragmented prairie environment of the Northern Great Plains. They cannot live by buds alone.
   

2. In addition to their winter values, food plots are readily used, and perhaps very important, as spring feeding areas for adults (males and females) and summer brood areas.
   

3. Providing winter food sources within management areas can minimize movements (and probably mortality) if optimum roosting habitat is in close proximity. Sunflowers are considered a premium winter food as far as preference and palatability. Corn and cereal grains are recommended as well.