Maricopa County (encompassing the greater Phoenix area) is as large as the state of New Hampshire with elevations ranging from 700 to over 7000 feet. Habitat diversity is also great from lowland deserts to mountain slope conifer stands. When Birds of Arizona by Phillips, Marshall, and Monson was published in 1964, only 326 species were on the Maricopa County list. The first edition of Birds of Maricopa County, Arizona by Demaree, Radke, and Witzeman, published in 1972, added 20 additional species. By the time Birds of Phoenix and Maricopa County, Arizona by Witzeman, Demaree, and Radke was published in 1997, 81 species had been added to the County list. This was mainly the result of the surge in the number of birders and the interest in birding in Arizona that began in the 1970s. Since 1996, the number of birders, the areas covered, and the frequency of coverage have all continued to increase. During that time there have been numerous changes, not only in the status of species, but in earlier or later arrival and departure dates, as well as new nesting records. These changes will all be incorporated in a revised and updated edition of Birds of Phoenix and Maricopa County, Arizona that is now in the process of being written.