Waterfowl Response to Rest-Rotation Grazing

Abstract

Waterfowl production on the stock-water reservoirs in the Milk River Association Allotment, Phillips County, Montana, was studied during 1973 and 1974 to evaluate the influence of rest-rotation grazing management. The breeding pair population increased by 42 percent, from 190 to 270 pairs, and brood production increased by 50 percent, from 127 to 191, during the study. Breeding pairs, broods, and species diversity increased on the allotment since 1970. Changes in the distribution of breeding pairs and broods suggested a positive response by waterfowl to the previous year's rest treatment, and a negative response to heavy grazing pressure during the late summer and fall of the previous year. Waterfowl responded positively to rest and deferred treatments, and negatively to spring grazing during the current season. Shoreline and upland transects established during 1974 indicated that new vegetation accumulated most rapidly in those pastures deferred from early season grazing. The greatest accumulation of residual vegetation occurred in the pasture rested and the pasture grazed only during the spring. Regrowth, following relief from grazing, contributed to the accumulation of residual vegetation. J. WILDL. MANAGE. 40(1):60-68 The construction of stock-water reservoirs has provided waterfowl breeding habitat in regions where such habitat was sparse or absent (Bue et al. 1952, Smith 1953, Uhlig 1963). The importance of these reservoirs in the annual production of waterfowl results from the comparative stability of water levels between years (Bue et al. 1964), the relatively high rate of reproductive success associated with low population densities (Smith 1953, Rundquist 1973: 62), and the large area involved (Smith 1953). A potential conflict between waterfowl and grazing animals exists on these reservoirs. Bue et al. (1952) demonstrated that grazing by cattle reduced the nesting cover rating of the upland vegetation around stock ponds. Furthermore, the quality of the shoreline cover decreased with increased grazing intensity, resulting in a reduction in use by breeding pairs and broods. Kirsch (1969) found higher nest densities and nesting success on ungrazed than on grazed plots. Rest-rotation (Hormay and Talbot 1961) is a grazing system which employs periodic rest to achieve an improved range condition. A grazing formula may be designed for maximum livestock production, but it also may consider other land uses. Gjersing (1975) demonstrated higher reproductive success and increases in waterfowl production on two allotments managed with restrotation, as compared to control units with continuous grazing. This study was a further evaluation of waterfowl response to rest-rotation management and emphasized responses to the individual treatments of the grazing formula. Field data were collected during the summer of 1973 and the spring and summer of 1974. The author gratefully acknowledges R. L. Eng for project planning, field assistance, and advice during preparation of the manuscript; D. C. Quimby and W. R. Gould for critical review of the manuscript; and F. M. Gjersing and J. D. Jones for project planning and field assistance.