California Gnatcatcher Habitat Evaluation Model [ds456]

This datalayer represents the final results of a habitat evaluation model for California Gnatcatcher (CAGN) in San Diego County. This model was used in the County of San Diego's Multiple Habitat Conservation Program (MHCP) to prioritize land acquisition for reserve design purposes (USFWS 2003) and has been used for monitoring of CAGN (Winchell and Doherty 2005). Data on California sagebrush habitat patch size and configuration, slope, and climate (temperature and precipitation) were used to generate this model. The resulting grid is mainly cartographic, and presents the results in the context of land cover that is not potentially habitat (development and agriculture) for CAGN. This datalayer was compiled and metadata created as part of the Southern California Data Integration Project. MODEL METHODS This model was developed by Technology Associates International Corporation (TAIC) (TAIC 2002). A grid poly feature class was created in attempt to determine the habitat patch size and spatial configuration of suitable CA sagebrush habitat for CAGN. Core areas (cells) of suitable sagebrush were selected where: a) the patch was within the "coastal" climate zone (average January minimum temperature above 5 degrees centigrade) and it contained a core area of at least 25 acres, or b) the patch was within the "interior" climate zone (average January minimum temperature below 5 degrees centigrade) and contained a core area of at least 50 acres. Next, satellite cells of suitable sagebrush were selected. These were areas of sagebrush habitat that are within 1600 feet distance of core cells (defined as distance traveled from non-core habitat to reach core areas). For this analysis, travel between core and satellite cells was not permitted over development; only over other habitat types and agricultural lands. The core and satellite areas were then combined to represent areas of high quality CA sagebrush habitat, which was then grown out to include contiguous areas of suitable sagebrush that were touching either core or satellite cells. The resulting grid was then scored as 0 for not-suitable habitat or 1 for suitable habitat. Next, areas with suitable slope were determined by selecting cells that were scored as suitable sagebrush that were on slopes less than 40%. The resulting grid from this step was scored as 0 for not-suitable habitat with a slope greater than 40% and 1 for suitable habitat with a slope less than 40%. For the next step of the model, climate coverages were manually prepared before the model runs. A 5 degree centigrade temperature cutoff was used to determine hot vs. cold from the average January minimum temperature. A value of 13.25 inches rainfall was used to determine wet vs. dry from the average annual rainfall. The results from this step were scored as 0 for not-suitable sagebrush habitats that were cold and wet, 1 for suitable sagebrush that was either warm and wet or cold and dry, and 2 for suitable sagebrush that was warm and dry. These resulting data scores were summed to create three sagebrush habitat type classifications: low, medium, and high. Low quality habitat (scored as 0) was identified as non-suitable vegetation types, developed, agricultural, or coastal sage scrub habitat that was cold and wet. Moderate quality habitat (scored as 1) was identified as sagebrush habitat that was either warm and wet or cold and dry. High quality habitat (scored as 2) was identified as sagebrush habitat that was warm and dry. The resulting values were reclassified to a 4 point ranking: very high (3), high (2), moderate (1), low or none (0). The low/ none classification was further expanded to other low quality habitat (5), developed lands (8), and agricultural lands (9). This model was developed in ArcINFO 8.0.2 as a grid file type. It is projected in NAD83 UTM Zone 11. REFERENCES Technology Associates International Corporation. 2002. California gnatcatcher habitat evaluation model for USFWS. Digital Data. USFWS Office. Carlsbad CA. Winchell, C. and P. Doherty. 2005. Estimation of California Gnatcatcher Pair Abundance and Occupancy Rates. Report Prepared for: California Department of Fish and Game, December 2005. U.S. Fish and Wildlife Service (USFWS). 2003. Proposed Rule: endangered and threatened wildlife and plants; designation of critical habitat for the coastal California gnatcatcher (Polioptila californica californica) and determination of distinct vertebrate population segment for the California gnatcatcher (Polioptila californica). Federal Register 68: 20228-20261.

Disclaimer : The State makes no claims, promises, or guarantees about the accuracy, completeness, reliability, or adequacy of these data and expressly disclaims liability for errors and omissions in these data. No warranty of any kind, implied, expressed, or statutory, including but not limited to the warranties of non-infringement of third party rights, title, merchantability, fitness for a particular purpose, and freedom from computer virus, is given with respect to these data.

This model used presence only data collected without considering closure, detection probability or probability-based sampling issues, and therefore is biased toward areas where gnatcatchers have higher detection probabilities (Winchell and Doherty 2005). The USFWS does not warrant the accuracy of this data, nor should it be used to represent the actual quality of gnatcatcher habitat through the extent of this data. For results and discussion of the ground-truthing of this model, see Winchell and Doherty 2005. Recommended Citation: Technology Associates International Corporation (TAIC). (Fall, 2002). California gnatcatcher habitat evaluation model [ds456]. Digital Data. Biogeographic Information and Observation System (BIOS). Retrieved on DATE from http://bios.dfg.ca.gov.