Climate change is predicted to exacerbate the effects of disturbances such as drought on numerous wildlife communities. on the basis of surveys from 1981 to 2014, we investigated whether drought altered the species richness and composition of bird communities of coastal sage scrub in two protected areas of southern California. at one site, the voorhis ecological reserve, Pomona, we found that the number of species of permanent residents, but not of summer and winter visitors, was lower during droughts than during periods of at least average rainfall. at the other site, the Bernard Field station, Claremont, we found that the richness of resident species remained the same in both drought and nondrought periods, and richness of summer and winter visitors increased during times of drought. the difference in patterns
between these sites may be explained by the presence of a constructed, permanent water source at the second site. thus, supplemental water sources embedded in natural areas might be an important resource for native bird species during drought.