In a Western ponderosa pine savanna, tall pines dot an open, grassy landscape. A Western Bluebird flits from a gnarly branch, as this Cassin's Finch belts out a rapid song. The trees here grow singly or in small stands. Upslope, the pines become denser, mixing with firs. Downhill, the trees give way to an open grassland. The open structure of this savanna, found on mountain slopes from the Rockies to the Cascades, results from recurring natural fires. Fast-moving blazes sweep through, burning the low vegetation but sparing the larger trees, which are protected by very thick bark. After a fire, grass and wildflowers re-grow quickly. Learn more at BirdNote.org.