young rufous-crowned sparrow leaves the nest after eight or nine days, it is still incapable of flight, though it can run through the underbrush; during this time it is still fed by the parents. Juveniles tend to leave their parent's territory and move into adjacent habitat in autumn or early winter. Reproductive success varies strongly with annual rainfall and is highest in wet El Niño years, since cool rainy weather reduces the activity of snakes, the main predator of the sparrow's nests. Conservation The rufous-crowned sparrow is treated as a species of least concern, or not threatened with extinction, by BirdLife International due to its large geographical range of about , estimated population of 2.4 million individuals, and lack of a 30% population decline over the last ten years. In years without sufficient rains, many birds fail to breed and those that do produce fewer offspring. Some of the local populations of this bird are threatened and declining in number. The island subspecies and populations have declined in some cases: A. r. sanctorum of the Todos Santos Islands is believed to be extinct, and the populations on Santa Catalina Island and Baja California's Islas de San Martin have not been observed since the early 1900s. Populations of the species in southern California are also becoming more restricted in range because of urbanization and agricultural development in the region. Additionally, the sparrow is known to have been poisoned by the rodenticide warfarin, though more research is needed to determine the effects of pesticides on the rufous-crowned sparrow. References Further reading External links Old illustration of the "Brown-headed Finch" from Cassin's Birds of California and Texas rufous-crowned sparrow Native birds of the Plains-Midwest (United States) Native birds of the Southwestern United States Fauna of the California chaparral and woodlands Birds of Mexico Birds of the Sierra Madre Occidental Birds of the Sierra Madre Oriental Birds of the Sierra Madre del Sur Birds of the Trans-Mexican Volcanic Belt Near threatened fauna of North America rufous-crowned sparrow rufous-crowned sparrow