Several authors have commented on the expanding range of the Mockingbird (Mimus polyglottos) in California (Seymour 1978; Legg 1959). Grinnell (1911) first reported an expanding population of the Mockingbird in California, followed by my paper 23 years later (Arnold 1935). The present paper reports continuing range expansion and speculates on the factors influencing this expansion.
Figure 1 shows the approximate range of the Mockingbird in California in 1978. This map does not indicate the many scattered fall and winter records.