Bobolink (Dolichonyx oryzivorus) Declines Follow Bison (Bison bison) Reintroduction on Private Conservation Grasslands

Abstract

Among the most rapidly declining birds in continental North America, grassland birds evolved with American bison (Bison bison) until bison nearly became extinct due to overhunting. Bison populations have subsequently rebounded due to reintroductions on conservation lands, but the impacts of bison on grassland nesting birds remain largely unknown. We investigated how bison reintroduction, together with other land management and climate factors, affected breeding populations of a grassland bird species of conservation concern, the Bobolink (Dolichonyx oryzivorus). We quantified population changes in Bobolinks over an 18-year period in conservation grasslands where bison were reintroduced, compared with adjacent grasslands grazed by cattle and where hay was harvested after the bird breeding season. Four years after bison reintroduction, the bison population in the study area had doubled, while Bobolink abundance declined 62% and productivity declined 84%. Our findings suggest that bison reintroduction as a conservation strategy may be counterproductive in grassland fragments where overgrazing, trampling, and other negative impacts drive declines in grassland breeding birds. Where bird conservation is an objective, small grassland reserves may therefore be inappropriate sites for bison reintroduction. To maximize conservation benefits to birds, land managers should prioritize protecting grassland birds from disturbance during the bird breeding season.

Arabian Partridge Abundance and Limiting Factors at the Northern Boundary of Its Range

“…Feral donkeys in the study area traveled in herds averaging 10 animals throughout the area, rather than along tracks or paths, distributing their impact throughout large areas. Previous studies have shown that livestock grazing may strongly affect birds, influencing their activity patterns, distribution, abundance, and/or nest success [31][32][33][34].…”

“…Increased grazing intensity may be associated with decreased bird densities, nest success, and recruitment [32,35]. In some respects, free-ranging domestic and feral livestock may partially fill ecological gaps left by the absence of wild grazers that have dwindled…”

“…Increased grazing intensity may be associated with decreased bird densities, nest success, and recruitment [32,35]. In some respects, free-ranging domestic and feral livestock may partially fill ecological gaps left by the absence of wild grazers that have dwindled or gone extinct in this region (such as the wild oryx and the gazelle), but their effects on habitat and native wildlife may be detrimental or unexpected [32,36]. Feral donkey grazing patterns have been shown to shift the composition of desert vegetation [37,38], negatively influencing habitat structure and function.…”

Can switches in disturbance type improve habitat for grassland birds in semi‐arid grasslands of South‐Eastern Australia?

“…In prairies of North America, large grazers ( Bison bison ) and prescribed fire have been reintroduced after >150 years, replacing livestock grazing, to restore a shifting pattern of disturbance across landscapes (Wilkins et al., 2019). Reintroduction of these historical processes alone has, however, not translated to positive outcomes for all grassland fauna (Burke et al., 2020; Kaplan et al., 2021). In some prairies, targeted livestock grazing has been found to be an effective substitute for bison‐fire interactions for maintenance of diverse habitats (Bailey et al., 2019; Derner et al., 2009).…”

The Potential of Bison Restoration as an Ecological Approach to Future Tribal Food Sovereignty on the Northern Great Plains

“…Bison are migratory herbivores that can and need to move across large landscapes (Bolger et al, 2008;Plumb et al, 2009), and by altering widespread vegetation structure and composition, bison grazing subsequently impacts prairie wildlife communities (Truett et al, 2001). However, when densities are manipulated and movements are constrained, the ability of the species to have positive impacts on the landscape may be limited (Boyce et al, 2021;Kaplan et al, 2021). Modern prairie conservation relies on the keystone traits of bison to restore ecological function of grasslands; therefore, conservation measures should explore ways to allow bison to move and migrate.…”