Published range maps are often used for conservation planning and biogeographical analysis. The range maps provided by NatureServe v. 3.0 seem to be the product most widely used for such purposes. In the case of songbirds, better range maps may exist for many species (e.g., in recently revised Birds of North America volumes) but digital versions are not generally available. We compared our Maxent predictions with the NatureServe products.
Models and occurrence records were overlaid with the published range maps and discrepancies and apparent range extensions were assessed visually. For all but three species, the BAM/BBS dataset contained occurrence records outside of NatureServe range map limits. This discrepancy is reflected in the Maxent model predictions. Thus, both occurrence records and model predictions may be used to refine the range limits for many species. All but nine species had data observations north of their published range limits.