Bird Foraging on Incense-Cedar and Incense-Cedar Scale during Winter in California

摘要

The response of birds to variations in the density of incense-cedar (Calocedrus decurrens, and through exclosure experiments, the impact of bird foraging on the density of the scale insect (Xylococculus macrocarpae), was studied in the mixed-conifer zone of the western Sierra Nevada during winter. Birds concentrated foraging activities on the bark of small (20 cm d.b.h.) cedar. Indices of abundance for many bird species were lower on sites with low-cedar density. Analysis of foraging activities indicated that birds reduced the density of scale insects on cedar and avoided sites with low-cedar density. The results indicate that a minimum density of 150 small cedar/ha may be required to prevent a reduction in the abundance of birds overwintering in these study areas. Small findings are contrary to current thinking of forest managers in the management of incense-cedar.