The effects of forest fragmentation on bird species abundance: a case study of the central high plateau of Madagascar

Abstract

Langrand, O. & Wilme, L. 2000. The effects of forest fragmentation on bird species abundance: a case study of the central high plateau of Madagascar. Ostrich 71 (1 & 2): 315. Considering the high rate of endemism in Malagasy organisms, which are mostly restricted to forest ecosystems, and the accelerating rate of deforestation, it is critical to understand the effects of forest fragmentation on Malagasy biota to allow for better management of species. The Ambohitantely Special Reserve, located on the central high plateau at 1 500 m asl, was selected as a study site for research on the effects of forest fragmentation on forest-department bird species in Madagascar. The forest, described as East Malagasy moist montane forest, is 2 737 ha in area, of which 1 487 ha make up 513 forest fragments scattered around the largest block totalling 1 250 ha. To investigate the effects of forest fragmentation on forest-dependent bird species, seven forest fragments were selected, ranging from 0.64 ha to 136 ha, in addition to the largest block, referred to as the control site. The relative abundance of a selection of bird species in the different-sized fragments was assessed in reference to the control site, by using a combination of two standardised sampling methods: mist-netting and point-counts. A total of 1 804 mist-net-days were accrued; 1 026 in the control site and 778 in the seven forest fragments, leading to the capture of 491 birds of 26 species. A total of 160 point-counts was made at 39 different sample plots totalling 53h 29 min of cknsusing, and a record of 30 species. The analysis of the relative abundance of bird species in different size fragments indicates a decrease in the number of forest dependent bird species and an increase in the generalist, or in non-forest dependent bird species, in relation to decreasing size of forest fragment.