Golden-Cheeked Warbler Hill Country Songbird REI has completed a number of studies evaluating plans for directing development practices in the habitat of endangered species. One such study assisted in the specification of policy for setting aside acreage to protect the nesting grounds of the Golden-Cheeked Warbler. The several studies led to the development of the Balcones Canyon Lands Conservation Plan in Travis County, Texas. The REI study is reported on the Environment Tab.