The avifauna within the Sky Islands of southeastern Arizona includes species found nowhere else in the United States, in part due to the availability of diverse habitats created by the mixing of Madrean and Cordilleran ecosystems. Neotropical migratory bird species visit these mountains, as well as many species typical of western North American montane forests. Birdwatchers from across the globe visit the region, providing a vibrant state and local ecotourism industry.
Within the last two decades, the Sky Islands have been under increased stress associated with ongoing droughts and wildfires. Nearly every mountain range in the region has been impacted by wildfires. The largest wildfire was the 2011 Horseshoe Two Fire, which burned 90,307 hectares of the Chiricahua Mountains.
RMRS scientists initiated a study in the 1990s on avian distribution and habitat associations within the Sky Islands. Objectives of the project include:
The project is funded through the U.S. Fish & Wildlife's Desert Landscape Conservation Cooperative.
RMRS scientists studied distribution, abundance, and habitat associations of forest birds across montane forest and woodland types in the Santa Rita, Santa Catalina, Huachuca, Chiricahua, and Pinaleño Mountains from 1991 to 1995 (Block et al. 1992, Sanderlin et al. 2013). This research included over 300 bird count stations and more than 1,200 habitat plots distributed across forest cover types (Iniguez et al. 2005).
Since the initial research, more than 80% of the bird count stations and vegetation plots were burned by wildfires. The initial RMRS project provides a unique and valuable opportunity to assess climate change and wildfire effects on bird habitats and populations, and the original data serves as a baseline for long-term monitoring.
Researchers are assessing the singular and synergistic effects of climate change and wildfire on avifauna using empirical avian habitat and population data and predictive climate change models. They resampled bird-count stations and vegetation plots in 2014 using the same protocols as the previous studies. This data allows researchers to quantify changes in habitat structure and composition and bird communities occurring over the 20-year period.
Southern Arizona is unique in having highly skilled citizens able to identify birds by sight and sound. These citizens are eager to assist with monitoring bird populations, but often are unfamiliar with design and implementation of rigorous monitoring programs.
RMRS scientists initiated a pilot study in 2012 in the Chiricahua Mountains to re-sample transects in coordination with Friends of Cave Creek Canyon, a non-governmental organization out of Portal, Arizona. This effort helped gauge volunteer workload and identify technical challenges.
A primary challenge was that many volunteers could not physically traverse the randomly-located RMRS transects. Therefore, researchers established new bird monitoring transects near trails and roads near the initial transects for 2013. New transects included points from the old transects when possible.
Study design guidelines exist for single-species occupancy models, but few recommendations exist for multi-species community occupancy models (Sanderlin et al. 2014). Statistical advances in Bayesian hierarchical multi-species occupancy models improve researchers’ ability to model data from multi-species monitoring programs, but there remains a trade-off between costs of increased effort from spatial and/or temporal replication and parameter accuracy of species richness and probability of occupancy, detection, and local colonization/extinction.
RMRS scientists are using simulation studies to inform optimal monitoring designs that can detect changes associated with large-scale stressors. Researchers are also extending their optimal design research for multi-species single-season occupancy models to multiple seasons. This will improve monitoring efforts and the ability to detect changes in species’ distributions from climate and wildfire events.
Results from this study will establish habitat correlates for numerous species. This information can guide management decisions during a fire event by identifying key habitats at risk or identifying critical habitats sensitive to climate change.
The habitat models resulting from this effort can also guide both pre-fire management to increase resilience of these forests to climate change and high-severity canopy fires, as well as guide post-fire restoration.
RMRS researchers are will work closely with local managers (Coronado National Forest, National Park Service, Department of Defense) to make results accessible through peer-reviewed publications and webinars supported by the Southwest Fire Science Consortium.
The citizen science bird surveys associated with this project also provide a model for long-term sustainable monitoring of avian communities. Citizen science resulted in inexpensive monitoring data and fostered greater local involvement in science and conservation. In addition, simultaneously resampling the existing RMRS transects will help researchers calibrate data from new transects and extend inferences to historical populations in the Sky Islands area.
Additional information on this project, including pictures and monitoring protocols, are available at the Arizona Sky Island Birds website.
Block, W.M., J.L. Ganey, K.E. Severson, and M.L. Morrison. 1992. Use of oaks by Neotropical migratory birds in the southwest. Pp. 65-70 in Ffolliott, P.F., G.J. Gottfried, D.A. Bennett, C. Hernandez, Ortega-Rubio, A., and R.H. Hamre, tech. coord. Ecology and Management of Oak and Associated Woodlands: Perspectives in the Southwestern United States and Northern Mexico. USFS Gen. Tech. Rep. RM-218. Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO.
Ganey, J.L., W.M. Block, J.S. Sanderlin, and J.M. Iniguez. In review. Nest site habitat of painted redstarts and red-faced warblers in the Madrean Sky Islands of southeastern Arizona.
Iniguez, J.M. 2000. Cover type and structural classification in the Sky Islands of southeastern Arizona. M.S. thesis. Northern Arizona University, Flagstaff, AZ.