The golden-cheeked warbler and black-capped vireo were listed by the U.S. Fish and Wildlife Service (USFS) as endangered in 1990 and 1987, respectively. In 1992 the 10,000 hectare Balcones Canyonlands National Wildlife Refuge (BCNWR) was established in the State of Texas to protect habitat for these two species. The warbler occupies later successional stages of oak and Ashe juniper woodland habitat during the breeding season while the vireo prefers early successional shrublands. Contemporary habitat models for songbirds often lack fine-scale habitat information mapped over large areas. Light detection and ranging (lidar) data and high spatial resolution National Agriculture Imagery Program color infrared (NAIP-CIR) aerial photography were used to characterize habitat structure and composition over the entire refuge. Habitat features such as successional stages, conifer and broadleaf tree canopy cover, tree density, and vertical and horizontal structural complexity were derived using machine learning and other statistical methods. Validation of the remote sensing applications indicated a strong relationship between field and lidar-derived tree canopy height (n=192, r=0.83) and percent canopy cover (n=95, r=0.97), characteristics that are important for modeling warbler and vireo occupancy. These data are being combined with 2012 breeding season songbird point count surveys to assess habitat occupancy across BCNWR and adjacent lands.
The study takes place on (A) Balcones Canyonlands National Wildlife Refuge, Texas, and uses (B) NAIP-CIR and discrete return lidar data to characterize songbird habitat features for oak and Ashe juniper woodlands.