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Open-File Report 2014–1050

Projecting Climate Effects on Birds and Reptiles of the Southwestern United States

By Charles van Riper III, James R. Hatten, J. Tom Giermakowski, David Mattson, Jennifer A. Holmes, Matthew J. Johnson, Erika M. Nowak, Kirsten Ironside, Michael Peters, Paul Heinrich, K. L. Cole, C. Truettner, and Cecil R. Schwalbe

Thumbnail of and link to report PDF (7.2 MB)Executive Summary

  • We modeled the current and future breeding ranges of seven bird and five reptile species in the Southwestern United States with sets of landscape, biotic (plant), and climatic global circulation model (GCM) variables.
  • For modeling purposes, we used PRISM data to characterize the climate of the Western United States between 1980 and 2009 (baseline for birds) and between 1940 and 2009 (baseline for reptiles). In contrast, we used a pre-selected set of GCMs that are known to be good predictors of southwestern climate (five individual and one ensemble GCM), for the A1B emission scenario, to characterize future climatic conditions in three time periods (2010–39; 2040–69; and, 2070–99).
  • Our modeling approach relied on conceptual models for each target species to inform selection of candidate explanatory variables and to interpret the ecological meaning of developed probabilistic distribution models. We employed logistic regression and maximum entropy modeling techniques to create a set of probabilistic models for each target species.
  • We considered climatic, landscape, and plant variables when developing and testing our probabilistic models. Climatic variables included the maximum and minimum mean monthly and seasonal temperature and precipitation for three time periods. Landscape features included terrain ruggedness and insolation. We also considered plant species distributions as candidate explanatory variables where prior ecological knowledge implicated a strong association between a plant and animal species.
  • Projected changes in range varied widely among species, from major losses to major gains.
  • Breeding bird ranges exhibited greater expansions and contractions than did reptile species.
  • We project range losses for Williamson’s sapsucker and pygmy nuthatch of a magnitude that could move these two species close to extinction within the next century. Although both species currently have a relatively limited distribution, they can be locally common, and neither are presently considered candidates for prospective endangerment.
  • We project range losses of over 40 percent, from its current extent of occurrence, for the plateau striped whiptail, Arizona black rattlesnake, and common lesser earless lizard. Currently, these reptile species are thought to be common or at least locally abundant throughout their ranges.
  • The total contribution of plants in each distribution model was very small, but models that contained at least one plant always outperformed models with only physical variables (climatic or landscape). The magnitude of change in projected range increased further into the future, especially when a plant was in the model.
  • Among bird species, those that had the strongest association with a landscape feature during the breeding season, such as terrain ruggedness and insolation, exhibited the smallest contractions in projected breeding range in the future. In contrast, bird species that had weak associations with landscape features, but strong climatic associations, suffered the greatest breeding range contractions. Thus, landscape effects appeared to buffer some of the negative effects of climate change for some species.
  • Among bird species, magnitude of change in projected breeding range was positively related to the annual average temperature of their baseline distribution, thus species with the warmest breeding ranges exhibited the greatest changes in future breeding ranges. This pattern was not evident for reptiles, but might exist if additional species were included in the model.
  • Our results provide managers with a series of projected range maps that will enable scientists, concerned citizens, and wildlife managers to identify what the potential effects of climate change will be on bird and reptile distributions in the Western United States. We hope that our results can be used in proactive ways to mitigate some of the potential effects of climate change on selected species.

First posted April 7, 2014

For additional information, contact:
Contact Information, Southwest Biological Science Center
U.S. Geological Survey
2255 N. Gemini Drive
Flagstaff, AZ 86001

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Suggested citation:

van Riper, C., III., Hatten, J.R., Giermakowski, J.T., Mattson, D., Holmes, J.A., Johnson, M.J., Nowak, E.M., Ironside, K., Peters, M., Heinrich, P., Cole, K.L., Truettner, C., and Schwalbe, C.R., 2014, Projecting climate effects on birds and reptiles of the Southwestern United States: U.S. Geological Survey Open-File Report 2014‒1050, 100 p.,

ISSN 2331–1258 (online)


Executive Summary




Summary of Results

Insert 1: Detailed Project Justification and Methods

Insert 2: The Southwestern NCCWSC Advisory Team Development

Insert 3: Bird and Reptile Distribution Data

Insert 4: Explanatory Variables

Insert 5: Modeling Plant Species Distributions

Insert 6: Modeling Bird Distributions

Insert 7: Modeling Reptile Distributions

Insert 8: Data Storage and Delivery

Insert 9: Website Application

Insert 10: Bird Species Count

Insert 11: Reptile Species Accounts

References Cited

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