Assessment of managed grazing systems for productivity and abundance in non-game birds
Christie, K. Rhian
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A primary objective of the North American Waterfowl Management plan is to encourage multipurpose programs that will provide long-term benefits to waterfowl and many other species while at the same time permitting some agricultural return. The purpose of this study was to evaluate one of these extensive programs, managed grazing systems, and its ability to increase the productivity and abundance of grassland non-game birds. Managed grazing systems are believed to simulate effects of periodic grazing by bison, and could potentially provide substantial benefits to both game and non-game birds. Twenty and seventeen managed grazing systems sites were monitored for two field seasons, (1995, 1996), respectively, and compared with 18 (1996) and 17 (1995) continuous or season-long grazing sites. Study plots were evaluated to compare non-game bird species abundance, richness, and productivity for any differences between the two grazing regimes. Circular plots with a 100-m radius were used in both treatment and control sites. Vegetation physiognomy was evaluated to determine the influence on species abundance and productivity. Emphasis was also placed on the management of each system and whether a particular landowner's method of management was conducive to increasing vegetation cover. Results indicate that managed grazing does not increase non-game bird species abundance or species richness. Average non-game species productivity for managed grazing systems did not differ from season-long grazing systems in 1995, but in 1996 significant differences in non-game bird productivity were detected. Some vegetative differences in percent bare soil, vegetation height and grass to forb ratios were noted between season-long and managed grazing. Finally, there was a large difference in non-game species abundance and productivity between the two field seasons.