Geographic Analysis of California Condor Sighting Data

Abstract

Observation and habitat data were compiled and analyzed in conjunction with recovery planning for the endangered California Condor (Gymnogyps californianus). A geographic information system (GIS) was used to provide a quantitative inventory of recent historical Condor habitats, to measure the association of Condor activity patterns and mapped habitat variables, and to examine spatio‐temporal changes in the range of the species during its decline. Only five percent of the study area within the historic range is now used for urban or cultivated agricultural purposes. Observations of Condor feeding perching, and nesting were nonrandomly associated with mapped land cover, in agreement with life history information for the species. The precipitous decline in numbers of Condors in this century produced only a small reduction in the limits of the observed species’ range, as individual birds continued to forage over most of the range. Some critical risk factors such as shooting and lead poisoning are difficult to map and have not been included in the database. Besides the applications demonstrated in this case study, GIS can be a valuable tool for recovery planning, in the design of stratified sampling schemes, or for extrapolation of habitat models over unsurveyed regions. We conclude with recommendations from this case study regarding when to consider using GIS and the importance of pilot studies and sensitivity analysis.

Habitat-Distribution Modeling of a Recolonizing Black Bear, <em>Ursus americanus</em>, Population in the Trans-Pecos Region of Texas

“…Often there is a strong locational bias, with higher sampling rates in the most accessible sites (Davis et al 1990). There can also be an issue when only a few individuals exist in a population, because this limits the number of independent sightings and lowers the power of statistical inferences (Stoms et al 1993). Although using sighting data to develop a model of potential habitat has its disadvantages, our validation procedures indicated our model is robust.…”

GIS as a Rapid Decision-support Tool for Raptor Conservation Planning in Urbanising Landscapes

“…Geographical context: spatially explicit surrogates using available data and communitybased sightings Elements of the natural and built environment, combined with readily available community-derived observational databases, once standardised and replicated over time, provide a first approximation of wildlife habitat use and distribution (Saunders 1993;Stoms et al 1993;Palma et al 1999;Lunney et al 2000;Thiele et al 2004). In compiling The New atlas of Australian birds, species presence data were collected during field surveys by members of amateur and professional birdwatching networks.…”

“…Although beyond the scope of this pilot study, it is important to assess the accuracy of the source data before including them in a GIS given the additive effect of errors when multiple data sets are overlayed (Bernhardsen 2002). An initial sensitivity analysis might confirm where data uncertainties are excessive for the application (Stoms et al 1993).…”

Ecological niche modelling and prioritizing areas for species reintroductions

“…For the condor large quantities (1,970 unique localities) of georeferenced occurrence data were provided by the authors of a previous analysis (Stoms et al, 1993), including data from museum specimens, historical sightings, and recent sightings of the species prior to its extinction in the wild and subsequent reintroduction in California. For the wolf, 26 occurrences were assembled from museum collections' databases (US National Museum of Natural History, University of Kansas Natural History Museum, Museum of Vertebrate Zoology, Instituto de Biología of Universidad Nacional Autónoma de México, University of Michigan Museum of Zoology) and six recent auditory records in remote regions (J. Servín, unpubl.…”