I conducted 18 eggshell removal trials at six Mountain Plover (Charadrius montanus) nests in the Pawnee National Grassland, Weld County, Colorado, during June 1994. Eggshell fragments were placed at various distances (10 cm to 10 m) from active nests. Attending adult plovers removed eggshells throughout the incubation period. When eggshells were placed within 2 m of the nest, plovers usually removed them immediately upon their return to the nest. Shells placed farther away—up to 10 m—were removed after longer time intervals. Plovers removed shells by picking them up with their bills and running or flying away with them before dropping them 6 to 100 m from the nest. When returning to their nests, plovers approached by ground. Of the five hypotheses proposed in the literature to explain the function of eggshell removal behavior in birds, only one (reducing cues predators might use for finding nests) predicts removal of shells already outside the nest and disposal of shells far from the nest. Thus, my results support an anti-predator function for eggshell removal in Mountain Plovers.