Landbird monitoring in the Northern Colorado Plateau Network: 2011 field season

Fogg, Jora

This report documents the results of the seventh year of habitat-based landbird monitoring in the Northern Colorado Plateau Network, which the Rocky Mountain Bird Observatory completed in 2011. In 2011, the Rocky Mountain Bird Observatory (RMBO), in cooperation with the National Park Service, completed the seventh year of a habitat-based landbird monitoring program in national parks of the Northern Colorado Plateau 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 is also consistent with goals emphasized by the U.S. North American Bird Conservation Initiative Committee (USNABCIMS 2007). In 2011, RMBO staff surveyed 45 transect locations within 11 NCPN units, placing 15 transect locations in each of the three habitats of interest: low-elevation riparian, pinyon-juniper, and sage shrubland. To increase sample size, all transect locations were surveyed twice during the breeding season. Using a modified monitoring design, staff also conducted four point counts two times each, as well as four area searches at Pipe Spring National Monument. This year, RMBO completed 100% of the assigned surveys with 94 transect visits between May 7 and July 7. A total of 9,626 birds of 115 species were recorded. The monitoring crew detected 2,997 birds of 85 species in low-elevation riparian, 2,850 birds of 76 species in pinyon- juniper, and 3,493 birds of 88 species in sage shrubland habitat. At Pipe Spring National Monument, observers detected a total of 286 birds of 36 species. The crew recorded one new species (bobolink) at Dinosaur National Monument. Density estimates were generated for species with more than 80 independent detections from 2005 to 2011. This year, density estimates were calculated for 57 species in at least one habitat. The data yielded robust density estimates (coefficient of variation (CV) < 50%) for 40 species in 2011. The RMBO staff expects to reach the target of detecting a population change of at least 3% within 30 years for these 40 species. The crew recorded 44 bird species of conservation or management concern throughout the network, and calculated density estimates for 24 of those species. Because seven years of data have been collected, the minimum number of detections used to estimate densities was increased from 60 to 80, following recommendations by Thomas and others (2010). Making this change initially decreased the number of species with density estimates but will provide more reliable estimates over time. A second year of trend analyses was conducted for those 25 of 44 species of conservation or management concern. Separate analyses were performed for each habitat. Significant trends were detected for 12 species. The results for several species differed from those obtained in 2010. For instance, black-billed magpie in sage shrubland habitat went from a negative trend in 2010 to a quadratic trend in 2011. Bewick’s wren continued to decline in pinyon-juniper. Long-term monitoring will be necessary for interpreting population status and trends for avian species of the NCPN.

Landbird monitoring in the Northern Colorado Plateau Network: 2011 field season

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