Nest predation on black-tailed prairie dog colonies

Nest predation is the principal cause of mortality for many grassland birds . Predation rates may be higher on prairie dog colonies because they may ha ve less available nesting cover and may increase predator abundance. We com pared 14-day nest predation rates for 1,764 artificial nests on 102 black-t ailed prairie dog (Cynomys ludovicianus) colonies and their paired off-colo ny sites (similar habitat lacking prairie dogs) from 14 May to 26 June 1998 in South Dakota and Wyoming. Predation rates on colonies (66.2 +/- 2.2%; ( x) over bar +/- SE) were 29.5% higher than at off-colony sites (51.1 +/- 2. 7%). Nesting cover on colonies was less dense and more uniform in structure and regression analysis showed differences in nest predation rates were co rrelated with estimates of mean nesting cover. Avian species associated wit h prairie dog colonies had smaller clutches and more broods/year than speci es associated with off-colony sites, suggesting a mechanism that may help c ompensate for increased risk of nest failure. Factors that influence predat or-prey dynamics (e-g., habitat fragmentation) or foraging success (e.g., i nsect availability) also may help explain higher risk of nest predation on prairie dog colonies. Our conclusions support others in recommending protec tion of large, intact prairie dog ecosystems.