Test of the Low Resolution New Mexico Topographic Spotted Owl Habitat Model in the Southwestern US

Johnson, Terrell

The statewide topographic model of potential of Mexican spotted owl (Strix occidentalis lucida) habitat in New Mexico (Johnson 1993) was derived from US Geological Survey (USGS) 1-degree Digital Elevation Model (DEM) data, based on 160 spotted owl territorial and 171 spotted owl roost locations known in New Mexico in 1991-92. The statewide model was reformulated for higher resolution 7.5-minute DEM data in northern New Mexico (Johnson 1996), based on just 37 territorial and 38 roost locations that were known in and around the Santa Fe National Forest in 1995. Small revisions to the statewide 1-degree DEM habitat model were also made at the same time, based on the original set of 1991-92 locations. Neither model has been systematically tested beyond its original data set. Both topographic models of spotted owl habitat in New Mexico yield an index that ranges from 1 to 1000, with higher indices implying better potential habitat. Because they are based only on topographic and geographic data, they are not complete, and only represent potential habitat. Both models are limited by the size and extent of the sample of known habitat that they describe and the topographic parameters available to the description. The test of any model is how well it performs on a new sample of known habitat. This report presents data on the performance of the 1-degree New Mexico model of potential spotted owl habitat, on an independent sample of spotted owl locations in New Mexico and on independent samples in Arizona, Utah, Colorado, and Texas. The 7.5-minute northern New Mexico model will be tested at a later date.