During the past 9 years, by use of artificial nest boxes, we have conducted studies on the life history of the Mountain (Parus gambeli) and Chestnut-backed (P. rufescens) chickadees and their impact on insect populations. Nine study plots consisting of 50 nesting boxes per plot at 100 m intervals (area of 50 ha) have been established in several montane regions of California (Dahlsten and Copper, unpublished manuscript).