Data linking climate change to observed changes in arctic marine and terrestrial wildlife populations are scarce, despite substantial changes in sea ice and arctic vegetation that constitutes wildlife habitat. Here, we mine observational records from the Alaskan Arctic to identify changes in distribution or behavior of many terrestrial wildlife species during the last century. We show that the increase in productivity of arctic vegetation and expansion of deciduous shrubs resulting from longer and warmer summers starting in the mid-1800s triggered the establishment of novel tundra herbivores moose in the 1930s and snowshoe hares in the 1970s, both which depend on shrubs protruding above the snow for forage in winter. Earlier spring onset has led to a 3-10 day earlier return of 16 species of migratory birds since 1964, though the effect of the altered timing on population sizes is unknown. Complicated interactions associated with predation, disease, trophic mismatch, competition, and other factors compromise predictions, underscoring the need to analyze observed wildlife changes and to maintain long-term studies.