It is hardly surprising that California—with its large size, seacoasts, and varied topography—would harbor one of the most diverse assemblages of birdlife of any state. The number of species recorded within its boundaries is exceeded only by that of Texas—and the difference is small. Grinnell and Miller (1944) recognized 427 species as having occurred naturally. Adjusted for the inclusion of introduced species, shifts in taxonomic concepts (AOU 1957, 1973, 1976), and critical reexamination of some early records (McCaskie et al. 1970), the 1944 list contains 431 species.
In the subsequent 3½ decades, the state list has continued to increase at an astonishing rate, and by the end of 1979 stood at approximately 535 species, a 24% increase.
Species recorded in the state for the first time since 1944 are listed in Table 1. In Table 2, I have divided this time period into several intervals and attempted to discern the probable source area for each of the additions: North American, Mexican, Arctic/Asian, or Pelagic. These categories are broad and occasionally overlap