USE OF AN EXOTIC TREE PLANTATION BY BORNEAN LOWLAND FOREST BIRDS

During May to July 1982, we surveyed birds in primary forest and in di fferent-aged groves of the exotic tree Albizia falcataria at Sabah Sof twoods, a lowland tree plantation in Sabah, East Malaysia (formerly Br itish North Borneo). We found that the Albizia was in general attracti ve to many native birds. About 60% of primary-forest species used the plantation, and the frequency at which individuals were observed in th e oldest groves was almost twice that of nearby primary forest. The Al bizia attracted birds because, as an extremely fast-growing legume wit h thin leaves, it permitted the rapid development of a well-structured secondary forest. It also was heavily infested with pest insects, whi ch provided an abundant food source. Despite its apparent richness, ho wever, the Albizia lacked several important features of natural forest (e.g. canopy fruits and nest holes). As a result, some primary-forest bird groups were poorly represented (e.g. large canopy frugivores and flycatchers) and others could make only limited use of the plantation (e.g. woodpeckers). In addition, the Albizia is expected to lose its diversity as the plantation as a whole ages. Many of the plantation bi rds were transients from nearby forest that visited daily to feed, and some probably had been displaced by intense logging. The number of da ily transients should decrease as primary forest recedes due to loggin g and development. Refugee species diversity should suffer from attrit ion as the plantation is cropped and predation and age take their toll .