Definition: Treeless, level, or gently rolling plains characteristic of arctic or subarctic regions, having a permanently frozen subsoil, and usually supporting low growing vegetation such as lichens, mosses, and stunted shrubs.
Definition: Type of food comprising the majority
of the diet of an animal.
Attribution: Richard M. Sibly, Christopher C. Witt, Natalie A. Wright, Chris Venditti, Walter Jetz, and James H. Brown. 2012. Energetics, lifestyle, and reproduction in birds. PNAS 109(27):10937-10941, doi:10.1073/pnas.1206512109