Western Tanager is a colorful, migratory songbird that is a common breeder in forests throughout much of the montane West, and spends the winter months in the forests of western Mexico. Watch for its quick arrival on the breeding grounds in late April, and the more protracted departure in fall migration, which spans July to late October.
The model performs exceptionally well for this species, and we believe these maps are accurate representations of where and when Western Tanagers occur in the United States. While some species (e.g., Mourning Dove or Red-tailed Hawk) do not have specific habitat associations, Western Tanager generally prefers pine forests for breeding. They do not breed in desert habitats, so their breeding range in the West is strongly defined by elevation and rainfall, and the tanagers are found in mid- to upper elevations in the Rocky Mountains and Sierra Nevada ranges. The fine-scale accuracy of the model is probably largely due to the fact that the habitat layers used for the models closely match the actual habitat preferences of the species. In general STEM maps do very well with evergreen specialists, like Western Tanager and (in the East) Brown-headed Nuthatch, since one of the key layers defines this forest type quite well. During migration (April, and September – October in particular) Western Tanagers occur in a variety of western habitats, including urban and suburban parks, deserts, and even patches of trees in grasslands.
During the breeding season, the map appears to focus on the montane forests, when the migrants arrive at their breeding grounds. The pressure to arrive at breeding areas and claim territories causes the spring migration to occur relatively rapidly, as compared with the more protracted fall migration. Fall migration in Western Tanager actually begins in early to mid-July, when the first adults return to Mexico. From August to October, migration brings Western Tanagers back to the lowland areas that they use in spring, but notice how much more slowly their overall departure progresses.