Cattle stocking rate and grazing duration effects on songbird nest survival vary by species in mixed-grass prairies

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Pipher, Emily
Curry, Claire M.
Koper, Nicola
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Grassland bird species are declining more quickly than birds of any other biome in North America, but the effects of the most widespread use of native mixed-grass prairies, livestock grazing, on nest survival of songbirds is not well understood. We used an adaptive management grazing experiment in southwestern Saskatchewan to evaluate effects of cattle stocking rate and number of years grazed on nest survival of five songbird species in 2009 and 2010. Two 300-m² plots were located in each of 12 pastures. Three pastures were ungrazed controls, while the remaining pastures had stocking rates ranging from 0.23-0.83 Animal Unit Months (AUM) · ha-1 (very low to very high for this region), and were grazed for 2-3 or >15 years. Analyses were conducted using logistic exposure regression. We found few effects of grazing on nest survival. Exceptions to this pattern were that the lowest nest survival rates occurred at low-moderate grazing intensities with fewer years grazed for Sprague’s pipits (Anthus spragueii) in 2009, at low grazing intensities and longer grazing durations for chestnut-collared longspurs in 2009, and at moderate grazing intensities regardless of grazing duration for vesper sparrows in 2010. Cumulatively, our results suggest that in the short term, a wide range of grazing intensities are consistent with the conservation of grassland songbirds, and that a mosaic of grazing intensities across the prairie landscape would provide preferred habitat types for a variety of songbird species.
Chestnut-collared longspur, grasslands, logistic exposure models, nesting success, Sprague’s pipit, vesper sparrow
1. Pipher, E.N., Curry, C.M., and Koper, N. 2016. Cattle grazing intensity and duration have varied effects on songbird nest survival in mixed-grass prairies. Rangeland Ecology and Management, 69: 437-443.