To what extent are current adaptations of animals shaped by past adaptations, random events, or current necessities? Why do some species have exceptional adaptive and invasive abilities while their relatives go extinct unable to cope with environmental change? The principal investigator will address these questions by studying a bird species that over the past seventy years had successfully colonized much of North America, acquiring the widest ecological range of any living bird and a range of diverse beak morphologies that enables it to survive in new environments. Capitalizing on recently discovered developmental mechanisms that produce such diversity, the principal investigator proposes and tests a novel explanation of how complex structures, such as avian beaks, can evolve rapidly and reversibly. Over the last twenty years the principal investigator, in close collaboration with local ranchers, citizens, tribal councils of three Indian reservations, as well as college students, established a unique temporal sequence of study populations that span hundreds of miles on both slopes of the Rocky Mountain Continental Divide in Montana. This work has been broadly advertised because of the highly visible nature of bird invasions, the well-established local media contacts, and wide public involvement in this large-scale project. Further, the principal investigator will continue to capitalize on the specialized undergraduate recruitment program in the University of Arizona to train minority students in modern scientific approaches to real life biological problems of species invasion and adaptation.