Climatic changes Ecological disturbances Ecosystem management Forest ecology Grassland ecology Ponderosa pine Ecology Restoration ecology Songbirds Ecology Watershed management Wildlife conservation Bird populations Birds Conservation Birds Migration Desert animals Climatic factors Endangered species Climatic factors Rio Grande Valley (Colo.-Mexico and Tex.) Environmental conditions Arid regions plants Birds Behavior Birds Ecology Cowbirds Behavior Desert tortoise Climatic factors Ecology Ecosystem health Endangered plants Climatic factors Endangered species Environmental management Ferruginous pygmy owl Ecology Forest management Grassland plants Grasslands