No description available.

No description available.

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.

This study considered the long term effects and interaction between burning and grazing in the northern mixed-grass prairies on the grassland songbird community. Point counts were conducted to assess songbird species abundances in burned-grazed, burned-ungrazed, unburned-grazed, and unburned-ungrazed pastures along with habitat structure (litter depth, vegetation height and density) over a five year period; from the first year post burn in 2007 until the fifth year post burn in 2011. Generalized linear mixed models were used to analyse the interaction between year, burning, and grazing for songbird abundances and habitat structure. As time since burned increased, species abundances in burned-grazed pastures have become more similar with those in unburned-grazed while abundances in burned-ungrazed are becoming increasingly similar to those in unburned-ungrazed pastures. The effects of burning are different than those of grazing and both disturbances should be utilised in grassland management when possible.

The immediate aim of this study was to relate herbage availability, liveweight gain and stocking rate to one another under continuous and rotational grazing so that management recommendations could be formulated for Coastcross II Bermudagrass and kikuyu. In addition, these data would be used for an economic evaluation of growing out young beef animals on these two pasture species. The broad long term goal was to use this information to persuade farmers to make more use of planted pastures and thereby reduce the stocking pressure on the veld. Besides pursuing the primary objectives, the study offered an opportunity to make an observational assessment of the put-and-take technique for use in grazing trials. In relation to fixed stocking, variable stocking appeared to have no distinct advantage in this study. This conclusion is drawn from the fact that little success was achieved in applying put-and-take at a high level of precision. It was therefore recommended that future trials should make use of fixed stocking, except when variation in herbage availability is very large and predictable. In such cases the use of put-and-take would be warranted. Liveweight gain of animals was linearly related to herbage availability. In two seasons liveweight gain of animals on Coastcross was higher for continuous grazing than for rotational grazing at equivalent herbage availability, but in other seasons there was no difference between the two methods of grazing. At equivalent levels of herbage availability liveweight gain was higher in early summer than in late summer. Herbage availability decreased linearly witilin each season and on average, rotational grazing resulted in increasingly greater herbage availability than continuous grazing, as stocking rate was increased on Coastcross. However, no difference between the two grazing methods was evident on kikuyu. Finally, the relationship between liveweight gain and stocking rate was also described by a linear function. On average, the stocking rate at which maximum liveweight gain per ha occurred (SRmax) was higher for rotational grazing than continuous grazing on Coastcross, but not on kikuyu. However, no difference was evident between the two grazing methods in each season. During the study period annual rainfall varied from 506 mm to 990 mm. This offered a unique opportunity to examine the relation between some of the pasture production parameters measured and annual rainfall. The length of the grazing season and SRmax increased, but liveweight gain of animals at SRmax declined as annual rainfall increased. This caused seasonal liveweight gain at SRmax to increase initially, but then to reach a maximum and decrease as annual rainfall increased from 500 to 1000 mm. From this information it was possible to build two models which can be used to predict liveweight gain per ha and profit per ha from stocking rate and annual rainfall. These models can either be built into farm planning programmes or used directly by agricultural advisors. In tl1is thesis they have been used to show that there is a wide range in stocking rates and levels of annual rainfall within which it is possible to make substantial profits by grazing young beef animals on dryland pastures. This study has therefore provided forceful information which can be used to persuade farmers to make more use of planted pastures, and in so doing, conserve the veld. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1983.

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.

This study considered the long term effects and interaction between burning and grazing in the northern mixed-grass prairies on the grassland songbird community. Point counts were conducted to assess songbird species abundances in burned-grazed, burned-ungrazed, unburned-grazed, and unburned-ungrazed pastures along with habitat structure (litter depth, vegetation height and density) over a five year period; from the first year post burn in 2007 until the fifth year post burn in 2011. Generalized linear mixed models were used to analyse the interaction between year, burning, and grazing for songbird abundances and habitat structure. As time since burned increased, species abundances in burned-grazed pastures have become more similar with those in unburned-grazed while abundances in burned-ungrazed are becoming increasingly similar to those in unburned-ungrazed pastures. The effects of burning are different than those of grazing and both disturbances should be utilised in grassland management when possible.

Grassland birds are experiencing the most significant declines of any avian guild in North America. Grazing is an important tool to manage habitats for these species, as they respond to structural changes in vegetation, and grazing affects vegetation structure. I studied the impact of cattle stocking rates grassland songbird abundances, with upland and lowland habitats in Grasslands National Park, Saskatchewan, Canada, 2006 to 2012. I also examined relationships between songbird abundance and plant community composition. Generalized linear mixed models were used for analyses. Species differed in responses to increased grazing (0 to 0.85 AUM/ha); Sprague’s pipit responded negatively, whereas chestnut-collared longspur responded positively. Above average precipitation during the study likely reduced the grazing effects. Overall, a range of cattle stocking rates makes habitat available for a complete songbird community. Efforts focused on prairie conservation should manage grazing at stocking rates that produce habitats that are under-represented relative to surrounding grasslands.

No description available.

Thesis (M.S.)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Brett E. Olson. Includes bibliographical references (leaves 36-40).