Hepatic Tanager
Hepatic Tanager is a widespread tropical species with the northern limit of its range reaching the Southwestern United States. Although a few are present year-round, the species is migratory in the U.S., arriving in April and departing in October. It is commonest in southeastern Arizona and southern New Mexico, but occurs in low density north to southern Colorado, west to southern California, and east to west Texas.
While these occurrence models perform extremely well with widespread, common species, the model performance is often much poorer for rarer and range-restricted species. These models use a combination of regional habitat coverages with effort-controlled eBird observations to make predictions about species occurrence. These regions are arbitrary and overlapping, but they do provide boundaries for the model. When the distributional boundaries match closely with the actual occurrence boundaries for the species, the model performs well. In Hepatic Tanager, this appears to be the case, since the full extent of the species' range is shown without significant over-extrapolation or under-extrapolation. In other cases the regional-habitat analysis does not match well with the species' occurrence, and this may lead to cases of over-extrapolation and under-extrapolation. Elegant Trogon occurs in a similar region of the country as the Hepatic Tanager, but it is much more restricted in range and occurs only in southeastern Arizona. Our model results for Elegant Trogon, shown below, extrapolate their occurrence farther north into the Mogollon Rim (where they do not occur). As research continues with these STEM models, we hope to improve our results for these range-restricted species.
