Removal of bell miners Manorina melanophrys from Eucalyptus radiata forest and its effect on avian diversity, psyllids and tree health.

摘要

The removal of a colony of bell miners (Manorina melanophrys) from a Eucalyptus radiata forest in Victoria, Australia in June 1993 resulted in an immediate influx of other species of insectivorous birds and a short-term increase in avian diversity and abundance. The reduction of bell miner numbers at the site resulted in the remaining individuals ceasing to exhibit interspecific territoriality and eventually abandoning the site. This suggests that a critical minimum number of individuals is neededto defend a territory. Once bell miners were removed, an infestation of Glycaspis sp. psyllids at the site was devoured by the invading insectivorous birds. However, with the recolonization of bell miners the Glycaspis sp. population returned close to its former levels. The major reduction in the number of bell miners and psyllids at the site for a 10 month period did not lead to an improvement in tree health during the 2.5 years following the cull. Phytophthora cinnamomi was present at both the experimental and control sites suffering dieback, and may have been the primary cause of the trees ill-health and lack of recovery.