Description
In the Chihuahuan Desert, grassland deterioration continues to be one of the major problems facing ecosystem health (Savory and Parsons, 1980). Brush encroachment has infested large swathes of grasslands throughout the Chihuahuan Desert ecotone of the Southwestern United Stated and northwestern Mexico (Buffington and Herbel, 1965; Hastings and Turner, 1965, Van Auken, 2000). Increases in woody plant encroachment in semiarid grasslands can be attributed to many factors (see for example: Archer 1994; Archer et al. 1995; Archer et al. 1988; Bahre 1991; Bahre 1995; Belsky et al. 1999; Bush and Van Auken 1995; Fleischner 1994; Humphrey 1958; Milton et al. 1994; Neilson 1986; Polley et al. 1994; Schmutz et al. 1991; Van Auken 2000; Van Auken and Bush 1997; Van Devender 1995; Wiltzen et al. 1997). However, recent short-term impacts appear to be the result of enduring, high intensity herbivory by domestic livestock (Van Auken, 2000). Over-grazing reduces above ground grass and forb biomass, which increases woody plant establishment by enhancing seed production, seed dispersal, seedling establishment, plant longevity, and stand development (Archer, 1994; Archer et al., 1995). The objective of this study is to quantify grassland health using Mearns, scaled, and Gambel���s quail as indicators. Because these three quail species inhabit a diversity of distinct niches (ranging from grasslands to riparian corridors) within the Chihuahuan Desert, they appear to be ideal indicators of broad-scale ecosystem change resulting from overgrazing. We predict overgrazed grasslands will show decreased abundances of quail relative to ungrazed grasslands. Furthermore, we predict heavily grazed grasslands will show decreased diversity of grasses and forbs relative to ungrazed grasslands, which will be reflected by decreased diversity of seed/invertebrate material in quail crop samples. Grazed pastures will be quantified as any pasture heavily grazed within the preceding five years, whereas ungrazed pastures will be those free from grazing in the preceding five years. This study will be conducted on ranchlands within south-central New Mexico and the Trans-Pecos region of Texas on which we already have pre-existing quail research being conducted. We will compared quail abundance (estimated using pointing dogs and flush surveys) and diet (determined from crop samples) across species, treatments (grazed vs ungrazed), and seasons (fall, winter, spring, summer) using multivariate analyses of variance. We will then use resource selection function models as a predictive tool for future habitat needs and/or to predict population changes resulting from increasing or decreasing commercial livestock production in the Chihuahuan Desert. These models will further our understanding of the population status of these three desert quail species, and will highlight habitat partitioning between the species in addition to quantifying their respective habitat needs. This study will compliment and expand already existing research being conducted by the Borderlands Research Institute at Sul Ross State University. In addition to the partnership between the Borderlands Research Institute and Sul Ross State University, this project will improve partnership capacities with the Bureau of Land Management, Texas Parks and Wildlife Department, US Fish and Wildlife Service, NRCS, Quail Forever, Southern New Mexico Safari Club International, National Wild Turkey Federation, and the Texas Quail Coalition.