a juvenile type 2 red crossbill loxia curvirostra eats gravel high in the mountains of colorado

adaptation alpestris animal anthropogenic avian biology bird birding birds birdwatching carbon change climate closeup colorado conservation conservatism crossbill curvirostra distribution ecology environment eremophila extinction gases global gravel greenhouse habitat indicator juvenile loxia microevolution migration modeling mountains natural nature niche ornithology outside perched red richness science species temperatures threatened tourism type warmdwelling warming wild wildlife