Effects of Livestock Grazing on Duck Nesting Habitat in Utah

Abstract

Periodic vegetation disturbance is an important yet controversial tool for waterfowl managers. Some have reported livestock grazing removes residual vegetation and thus is detrimental to nesting ducks, and others argue that such disturbance is necessary to maintain grassland health. We evaluated the impact of winter livestock grazing on duck nesting at Bear River Migratory Bird Refuge, Utah. During winter 1999, 6 experimental plots were grazed by cattle and 6 were ungrazed; in winter 2000, 8 plots were grazed and 8 were ungrazed. All grazing treatments were conducted during 15 November-15 March and averaged a stocking rate of 9.5 animal unit months/ha. During the following spring nesting season, we measured visual obstruction readings (VOR) on grazed and ungrazed sites. Although VOR on ungrazed sites were greater than those on grazed sites, this difference became less important as the nesting season progressed. Winter grazing impacted the nesting habitat of early-nesting ducks such as mallards (Anas platyrhynchos), but not that of late-nesting species such as cinnamon teal (Anas cyanoptera) and gadwall (Anas strepera). When using livestock grazing to manage grasslands, waterfowl managers should consider their management goals, the species composition of breeding duck populations, and environmental conditions. ResumenEl disturbio perió dico de la vegetació n es una herramienta importante, pero controversial, para los manejadores de las á reas de há bitat de aves acuá ticas. Algunos han reportado que el apacentamiento del ganado remueve la vegetació n residual y que es prejudicial para el anidamiento de los patos, mientras que otros argumentan que tal disturbio es necesario para mantener la salud del pastizal. Evaluamos el impacto del apacentamiento del ganado en invierno sobre el anidamiento de los patos en el Refugio de Aves Migratorias Bear River, Utah. Durante el invierno de 1999, 6 parcelas experimentales fueron apacentadas por ganado y otras 6 no recibieron apacentamiento; en el invierno del 2000, 8 parcelas se apacentaron y otras 8 no; todos los tratamientos de apacentamiento se condujeron del 15 de Noviembre al 15 de Marzo con una carga promedio de 9.5 Unidades Animal Mes ha À1 . Durante la época de anidamiento en la siguiente primavera tomamos lecturas de la obstrucció n visual (OVR) en los sitios apacentados y sin apacentar. Aunque las VOR de los sitios sin apacentar fueron mayores que las de los sitios apacentados, esta diferencia vino a ser menos importante conforme la estació n de anidamiento progresó . El apacentamiento invernal impacto el há bitat de anidamiento de los patos que anidan temprano, como los ''Mallard'' (Anas platyrhynchos), pero no el de las especies que anidan má s tarde, como el ''Cinnamon teal'' (Anas cyanoptera) y el ''Gadwall'' (Anas strepera). Cuando se utiliza el apacentamiento del ganado para manejar el pastizal, los manejadores de las á reas de anidamiento de aves acuá ticas deben considerar en sus metas de manejo la composició n de especies de las poblaciones de patos...

Duck Productivity in Restored Species-Rich Native and Species-Poor Non-Native Plantings

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The use of digital photos to assess visual cover for wildlife in rangelands

“…Increased grazing pressure reduces the visual cover reading obtained by the Robel pole (Reese et al, 2001;West and Messmer, 2006). There is evidence that greater visual cover readings are found at bird nesting sites compared to non-nesting sites (e.g., Fondell and Ball, 2004;Pitman et al, 2005;West and Messmer, 2006). However, other studies which modeled habitat characteristics and included Robel pole readings in their initial site characterization found that the pole readings had little explanatory power (e.g Moynahan et al, 2006;Renfrew et al, 2005;Warren and Anderson, 2005;Winter et al, 2005).…”

“…The Robel pole was devised as a method to non-destructively estimate grassland productivity; it has since been adapted for measurement of habitat characteristics in relation to concealment in ground cover for small mammals and particularly birds (Robel et al, 1970). Increased grazing pressure reduces the visual cover reading obtained by the Robel pole (Reese et al, 2001;West and Messmer, 2006). There is evidence that greater visual cover readings are found at bird nesting sites compared to non-nesting sites (e.g., Fondell and Ball, 2004;Pitman et al, 2005;West and Messmer, 2006).…”

Impact of mining on herbaceous ground cover and wild fauna in Birsha- Damoh forest range a buffer zone of Malanjkhand Copper mines of India

“…According to Tripathi and Singh, (2012) harvesting of forest for mining and local demand for fuel leads to the development of grassland and increasing grazing pressure might have reduced the herbaceous ground cover (Singh, et al, 1991a, b, Reese et al 2001, West and Messmer 2006, Sanjari et al 2006). The grazing pressure might have affected soil properties due to forest degradation (Singh et.…”