Grazing Systems Do Not Affect Bird Habitat on a Sandhills Landscape

Grassland birds are declining faster than any other guild of birds in North America, in part because of degradation of their breeding habitat. Rangeland managers recommend increasing heterogeneity to improve biodiversity; however, on privately owned rangelands, beef production likely decreases heterogeneity on the landscape. One suggestion has been to use multiple grazing systems across a landscape to increase heterogeneity and provide benefits for avian biodiversity, but there is little research to support this recommendation. Thus, our goal was to examine heterogeneity and songbird abundance in relation to grazing systems used by private producers in a large, intact rangeland region. We measured vegetation structure and conducted avian surveys in the Nebraska Sandhills on 11 management units with five different grazing systems, including season-long continuous, deferred rotation, management intensive, dormant season only, and a fixed rotation. On each management unit we assessed the relationship between vegetation structure or songbird abundance and potential management effects, such as grazing system, stocking rate, and management intensity. Season of use and stocking rate were the most common sources of variation in vegetation structure and songbird abundance. Grazing system did not explain variation in vegetation structure or bird abundance, except for heterogeneity in live grass cover, litter cover, shrub cover, and abundance of field sparrows. Vegetation structure varied across the landscape we sampled, but the range of heterogeneity was narrow. Thus, managers should not assume that using a variety of grazing systems across a landscape will inevitably result in heterogeneity of vegetation structure. Rather, managers should focus on creating contrasting vegetation structure in large areas to increase large-scale heterogeneity. This may be achieved through the application of more extreme management practices (e.g., long-term heavy grazing and long-term rest or patch-burn grazing) so that a wider variety of vegetation composition and structure is available to support biodiversity.