Effects of cattle stocking rate and years grazed on songbird nesting success in the northern mixed-grass prairie.

摘要

Grassland bird species are declining more quickly than any other avian group within North America, possibly due in part to declines in nesting success. In 2009-2010, I monitored nests of five songbird species in southwestern Saskatchewan. Two 300-m2 plots were located in each of 12 pastures, three of which were ungrazed controls. The remaining pastures had stocking rates ranging from 0.23 – 0.83 AUM/ha, which were grazed for 2-3 or >15 years. Stocking rate affected nest site selection by three species, suggesting that some pastures have a greater availability of nest sites than others. Logistic exposure nesting success models suggested a nonlinear effect of stocking rate on nesting success of Sprague's Pipit in 2009. The nesting success of two species was negatively correlated with grazing duration in 2009 and 2010, respectively. To encompass the different habitat needs of each species, I suggest maintaining rangeland landscapes with a range of grazing treatments.