Effects of tropical rainforest fragmentation on bird species: a case study from the Bemanevika Protected Area, northwestern Madagascar

The effects of forest fragmentation on forest bird species in the Bemanevika Protected Area (PA), northwestern Madagascar, were investigated during two breeding seasons from October 2016 to January 2018. The forest of Bemanevika is composed of large patches of fragmented tropical rainforest. Seven forest fragments ranging from 10 to 1 050 ha were surveyed. Two methods were used to collect data along transects orientated from the forest edge toward the interior of the forest: mist-netting and point-counts. In all, 27 non-forest birds and 65 forest birds were recorded at all fragments. According to their distribution along an edge-interior gradient, these 65 forest species are classified into three main groups: 15 (23.1%) edge species, 12 (18.5%) forest interior species and 38 (58.5%) ubiquitous species. Larger forest fragments host more forest bird species than smaller forest fragments. Of the 65 forest birds, 14, including the 12 forest interior species, were not found in the four smaller fragments (10-29 ha). The density of forest interior species was positively correlated to forest fragment size. The general trend was that forest interior species were the most sensitive to forest fragmentation (e.g. Madagascar Serpent-eagle Eutriorchis astur, Pitta-like Ground-roller Atelornis pittoides and Schlegel's Asity Philepitta schlegeli). Large raptors, terrestrial species and understory species were the first to disappear from the small fragments. Fragmented forests provide habitat for bird species, even for those vulnerable to forest fragmentation, therefore the maintenance of large enough forest fragments should be considered in all conservation strategies aimed to protect forest birds.