Rabbitbrush is a common shrub in semiarid regions of the American West. For much of the year, it likely goes unnoticed by hikers and casual naturalists but, in autumn, its canopy of pungent, bright yellow flowers attracts everyone's attention.
By early winter, the flowers have faded to dull-colored seed heads and dense stands of rabbitbrush attract a variety of wintering songbirds, especially sparrows. The abundant seeds offer a plentiful source of food and the shrub's dome-like structure "shades" the ground from snowfall, providing open forage areas and refuge from predators. Here along the Colorado Front Range, white-crowned sparrows are often abundant in these stands in late autumn, replaced during the colder months by American tree sparrows, song sparrows and, on occasion, Harris' sparrows; spotted towhees, dark-eyed juncos, house finches and goldfinches (both American and lesser) also feed on or beneath the rabbitbrush.
Birders who visit South Platte Park, in Littleton, generally focus on the excellent diversity of waterfowl and raptors. Unless they stop along the trails to survey the rabbitbrush, they may miss the more reclusive songbirds.