Studies of avian reproductive success provide important clues about the relationship between a species’ population and its habitats. Although many species are hard to study because their nests are difficult to locate and assess, the Curve-billed Thrasher (Toxostoma curvirostre) is an ideal subject. Its open-cup stick nests are easy to find and often at a height convenient for observing nest contents. For the subspecies in southeastern Arizona (T. c. palmeri), the breeding season can begin in late January, but generally nesting does not increase sharply until late March, with a distinct peak from mid-April through mid-May (Corman 2005). The initiation of breeding, however, seems (in part) correlated with the amount of winter precipitation. Two or more wet months in succession lead to food resources sufficient to elicit early nesting (Smith 1971), but earlier clutches may be smaller than those laid later, as early in the season food supplies may be limited (Stahlecker 2003). As food supplies increase, clutch sizes increase (Smith 1971). On the other hand, the success rate of earlier nests may be greater, as important predators of eggs and nestlings, such as snakes, are less active early in the season (Tweit 1996). To assess the Curve-billed Thrasher’s nesting chronology and reproductive success after a period of abundant autumn–winter rainfall, I began a study of its nesting near Tucson, Pima County, Arizona, in late January 1979.