Rangewide Occupancy and Post-Fire Recovery of California Gnatcatchers in Southern California, 2020

Publication Date

2021-10-27

Start Date

2020-04-27

End Date

2020-07-30

Kus, B.E., and Houston, A., 2021, Rangewide occupancy and post-fire recovery of California gnatcatchers in southern California (ver 2.0, March 2023): U.S. Geological Survey data release, https://doi.org/10.5066/F7PC30JX.

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This project has two goals: 1. To conduct a statistically rigorous study of occupancy to determine the post-fire recovery of gnatcatchers and coastal sage scrub (CSS) vegetation with the goal of informing management before, during, and after fire. Specific objectives include: a. Determine whether there has been recovery of California Gnatcatchers in areas burned in 2003, 2007, and 2014. b. Determine if there is a difference in California Gnatcatcher occupancy between areas burned in 2003, 2007, and 2014. c. Determine the relationship between California Gnatcatcher occupancy and vegetation composition, cover and structure. d. Determine the composition, cover, and structure of CSS vegetation in areas with different fire histories and evaluate patterns of vegetation recovery based upon time since fire, spatial distribution, previous land use, and environmental conditions. 2. To conduct rangewide surveys to determine California Gnatcatcher occupancy at a regional scale. Because California Gnatcatchers will be managed through management of CSS rather than through species-specific actions, it is necessary to determine the current status of gnatcatchers on protected lands in southern California to understand how gnatcatcher occupancy is related to CSS plant composition, cover, and structure. This in turn will provide information on where and how CSS could be managed and restored to benefit California Gnatcatchers and other inhabitants. Specific objectives include: a. In 2016 and 2020, determine the percent area occupied (PAO) by California Gnatcatchers in modeled high and very high suitability habitat on conserved lands and on participating military lands in southern California. b. Over the next 15 years, determine long-term trends in California Gnatcatcher PAO and in their colonization and extinction rates in modeled high and very high suitability habitat on conserved lands and participating military lands in southern California and be able to detect at least 30 percent change in California Gnatcatcher PAO. c. Beginning in 2016, identify associations between habitat correlates with California Gnatcatcher PAO and with colonization and extinction rates in order to develop biologically meaningful thresholds for management and to specify management criteria and recommendations.

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• USGS Western Ecological Research Center

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