The ultimate goal of this research is to characterize bird habitat along North American Breeding Bird Survey routes to help explain why some bird populations have been declining in recent decades. The North American Breeding Bird Survey (BBS) was begun in 1966 by the U.S. Geological Survey to monitor trends in bird populations throughout the continent. Since that time, the program has expanded to include more than 3000 routes that are surveyed annually by professional biologists and skilled amateur bird watchers. The data accumulated from this large-scale survey are extremely valuable to government agencies, conservation organizations, researchers, and the general public. In addition to describing the range and size of bird populations, the survey data reveal whether declining populations in certain parts of the continent are part of a larger trend or simply a shift in the breeding range of a particular species. The primary goal of this research project is to conduct a pilot study of bird habitat along two BBS survey routes in southern California. The two routes chosen for this project are the Tujunga Route in the San Gabriel Mountains and the Green Valley Route in the San Bernardino Mountains.