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Predictive mapping of avian populations using texture indices based on digital orthophotos.
Pidgeon, Anna1, Radeloff, Volker1, Mathews, Nancy1, 1
ABSTRACT- The importance of broad scale processes on animal population dynamics is widely acknowledged, but comprehensive monitoring at broad scales is seldom feasible. However, maps of avian abundance and richness pattern across landscape are needed both as input for spatially explicit population models and as basis for conservation planning. New tools are needed to derive such maps. In arid ecosystems, avian species abundance and richness is highly correlated with vegetation structure and particularly nest site availability. We tested the power of image texture measurements derived from digital orthophotos as predictive variables for avian abundance and richness in the northern Chihuahuan Desert, NM. Texture measures were derived from digital orthophotos. We estimated gray value variance and range using a 3x3 window as well as local variograms to measure spatial autocorrelation pattern. The texture measurements were correlated with extensive field data collected at forty two 640ha plots during 1996-1998. Our results indicate that texture measurements are successful in identifying avian hotspots within a given habitat type (e.g., mesquite). However, additional information, such as a satellite classification is required to stratify a landscape with multiple habitat types. The increasing availability of land cover classification and of digital orthophotos makes our approach a promising new tool for landscape ecologists and conservation biologists.
KEY WORDS: landscape ecology, avian population, habitat mapping, desert