Loss of remnant trees causes local population collapse of endemic Grosbeak Starling Scissirostrum dubium in Central Sulawesi, Indonesia

Abstract

Large and isolated trees are often last refuges for rare forest species in highly fragmented and human-dominated landscapes. This is of particular importance in tropical forest margin areas where remnant forest trees are being cleared at an alarming rate. Drivers and consequences of such remnant forest tree losses are still poorly documented. Here we report the rapid destruction of remnant trees, closely associated with colonies of the Sulawesi endemic Grosbeak Starling Scissirostrum dubium, which excavates nest holes in large dead trees. In 2008, we mapped all the species's potential breeding trees, tree characteristics and the local population density on the east margin of Lore Lindu National Park, Central Sulawesi, Indonesia. When the area was revisited in 2010, we found a dramatic loss of 92% of the recorded nest sites, accompanied by a remarkable decline of the local Grosbeak Starling population. This study provides an alarming example of the immediate consequences of the loss of remnant forest trees in tropical human-dominated landscapes for species dependent on this habitat structure. Without the contemporary implementation of strategies maintaining a high density of isolated large trees in forest margin zones and adjacent cultivated areas, associated species will experience dramatic population declines and a high local and, in the mid-to long-term, a high regional risk of extinction.