Whitebark pine (Pinus albicaulis) is known to have its seeds harvested and cached in the soil by Clark's Nutcracker (Nucifraga columbiana), and unretrieved seeds are known to be capable of germinating and establishing new pines. Many other vertebrates also harvest and feed on these seeds, however, and the roles of these animals as dispersers and establishers of whitebark pine has been uncertain. This work demonstrates that birds other than the nutcracker, rodents, and other mammals do not have the requisite behaviors to systematically disperse or establish whitebark pine, and that the pine is therefore dependent on the nutcracker for its regeneration. These findings support previous suggestions that Clark's Nutcracker is a specialized frugivore that has profoundly influenced the ecology and the evolution of whitebark pine.