CATTLE TRAMPLING OF SIMULATED GROUND NESTS IN ROTATIONALLY GRAZED PASTURES

For many grassland songbird species, pastures represent some of the be st available breeding habitat in the Upper Midwest. Increasing interes t in intensive rotational grazing (IRG) among midwestern livestock far mers may result in an expansion of pasture hectares in the region. We evaluated the effects of several cattle stocking densities on ground n est survival in rotationally grazed cool-season pastures in southweste rn Wisconsin, Ground nests were simulated with clutches of 3 unwashed pheasant eggs. We tested 3 rotational grazing systems: a 1-day dairy r otation stocked at 60 head ha(-1) a 4-day beef rotation at 15 head ha( -1), and a traditional, non-intensive 7-day rotation at 8 head ha(-1). Paddock size (1.2 ha) and nest density (15 nests paddock(-1) were hel d constant. The simulated nests were observed 4 times day(-1) to docum ent trampling patterns during the herds' diurnal grazing and ruminatio n cycles. Trampling damaged a mean of 75% (+/- 3.1%) of the nests for all 3 treatments during 8 consecutive replications. While the 7-day tr eatment exhibited a pattern of greater nest trampling during cattle gr azing periods than during rumination periods, this pattern was less ev ident in the 4-day treatment and absent in the 1-day treatment. Increa sing vegetation height-density and percent vegetation cover were assoc iated with reduced nest trampling fates, but pasture forage production and removal were not associated with nest damage.