Introduction

The Canyon Towhee is a large, plainly marked sparrow of low vegetation and the ground. Showing no sexual color dimorphism, this sedentary permanent resident occurs widely throughout most of the Upper and Lower Sonoran zones of the temperate and subtropical North American Southwest to tropical Mexico. The most versatile of all towhees, the Canyon Towhee demonstrates wide geographic and ecological amplitudes, occurring in almost all habitats except heavily settled urban areas and wet riparian forests. Habitats selected by this species range from scrub along dry watercourses and upland desert scrub at lower elevations upward into higher-elevation pine-oak (Pinus-Quercus) or even coniferous forest. Even though geographically and ecologically more widely distributed than its close relative Abert’s Towhee (Pipilo aberti), the life history of Abert’s Towhee was known earlier and is still better known in many aspects than that of the Canyon Towhee.

The Canyon Towhee is an adaptable passerine, especially in habitat selection, vocalizations, and behavior. Extremely plastic in behavior, it ranges from a shy, seldom-seen species in rugged, remote regions to a dooryard human associate, as are the Cactus Wren (Campylorhynchus brunneicapillus) and Curve-billed Thrasher (Toxostoma curvirostre).

The Canyon Towhee and related species, especially those collectively known as brown towhees, serve as a model for studies in speciation (Davis 1951). Until recently, the Canyon Towhee and California Towhee (Pipilo crissalis) were treated conspecifically under the name P. fuscus (Brown Towhee). Mitochondrial DNA studies have assisted in settling the century-old conflict over the relationship of these two taxa with their numerous subspecies (Zink and Dittmann 1991). Relationships among these taxa are also a prime subject of the ongoing debate about the biological species concept versus the phylogenetic species concept (Zink and McKitrick 1995).

Canyon and Abert’s towhees have been included in numerous studies during the past 40 years in the vicinity of Tucson, AZ (Marshall 1960, 1964, Emlen 1974, Tweit and Tweit 1986, Johnson et al. 1987, Mills et al. 1989). The phylogenetics, vocalizations, and U.S. distribution of the Canyon Towhee have been studied extensively, but much of its life history is unknown, especially nesting and rearing of young. Metabolic, energetics, and time budget studies are yet to be completed for the Canyon Towhee, and its distribution throughout much of Mexico remains poorly known.