Landbird monitoring in the Northern Colorado Plateau Network: 2010 field season report

Rehm-Lorber, Jora; Hanni, David

This report documents the results of the sixth year of habitat-based landbird monitoring in the Northern Colorado Plateau Network, which the Rocky Mountain Bird Observatory completed in 2010. In 2010, the Rocky Mountain Bird Observatory (RMBO), in cooperation with its partner, the National Park Service, completed its sixth year of a habitat-based landbird monitoring program in the Northern Colorado Plateau Inventory and Monitoring Network (NCPN). This program is designed to provide rigorous population trend data on most diurnal, regularly occurring breeding landbird species throughout the network. This information is useful for land managers and supports the National Park Service’s goal of developing long-term monitoring of biological indicators for network parks. The program, Monitoring Birds of the National Park Service, Northern Colorado Plateau Network, is also consistent with goals emphasized by the U.S. North American Bird Conservation Initiative Committee (U.S. NABCIC 2007). RMBO surveyed 45 transects within 11 NCPN units, placing 15 transects in each of the three habitats of interest: low-elevation riparian, pinyon-juniper, and sage shrubland. To increase sample size, all transects were surveyed twice during the breeding season. Ten points were also conducted during the second year of a modified monitoring design at Pipe Spring National Monument. This year, 100% of the assigned transects were surveyed, with 94 transect visits completed between May 8 and July 13. Not counting low-density species detections (birds detected between points), a total of 9,313 birds of 113 species were recorded in all habitats in 2010. In low-elevation riparian habitat, 2,844 birds of 83 species were detected. In pinyon-juniper habitat, 2,961 birds of 80 species were detected. In sage shrubland, 3,315 birds of 85 species were detected. A total of 193 birds of 29 species were detected in Pipe Spring National Monument. One new species (pink-sided dark-eyed junco) that was previously noted as probably present was recorded at Colorado National Monument, and two new species were recorded (black phoebe and Eurasian-collared dove) at Pipe Spring National Monument. Data collected from 2005 to 2010 were pooled to generate density estimates for species with sufficient data. This year, density estimates were calculated for 60 species in at least one habitat. The data yielded robust density estimates (coefficient of variation <50%) for 41 species in 2010, and RMBO expects to reach its target of detecting a population change of at least 3% within 30 years for these 41 species. RMBO recorded 41 bird species that are of conservation and management concern throughout the NCPN, and calculated density estimates for 25 of those 41 species. With the NCPN program in its sixth year, trend analyses were also conducted for those 25 of 41 species of conservation and management concern. Separate analyses were performed for each habitat. Significant trends were detected for six species, four of which had positive trend detection (black-throated sparrow and lazuli bunting, in low-elevation habitat; and dusky flycatcher and sage thrasher, in sage shrubland habitat) and two of which had negative trend detection (Bewick’s wren, in pinyon-juniper habitat, and black-billed magpie, in sagebrush habitat). Populations appeared to be stable (no trend detected) for most species of conservation concern within the NCPN; however, Bewick’s wren, in pinyon-juniper habitat, and black-billed magpie, in sagebrush habitat, appeared to be experiencing significant declines, warranting further investigation. The trend was not significant for Bewick’s wren in low-elevation riparian habitat, although the density estimate in 2010 was the lowest estimated for the six years of this program. Long-term monitoring will continue to be necessary for interpreting population status and trends for avian species of the NCPN.

Landbird monitoring in the Northern Colorado Plateau Network: 2010 field season report

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