Forest fragments matter: a look into the species richness and diversity patterns of birds in a small, isolated, Protected Landscape in Mindanao Island, Philippines

Abstract

The establishment of Protected Areas is deemed of critical importance in global conservation initiatives, particularly in biodiverse regions and global biodiversity hotspots, such as the Philippines. However, the crucial role played by smaller Protected Areas in biodiversity conservation is frequently overlooked, making this a particular area of research interest. The Initao-Libertad Protected Landscape and Seascape (hereinafter – ILPLS) is one of the last remaining karst forests with natural vegetation and refuge for wildlife conservation on the island of Mindanao, the Philippines. However, the landscape component of this Protected Area is very small (ca. 506 000 m2), bisected by a road, and heavily disturbed by illegal logging and frequent tourist visits. From 2014 to 2018, we assessed the community structure and revealed patterns of bird diversity in ILPLS. We recorded a total of 814 individuals of birds from 36 species and nine feeding guilds from a total sampling effort of 558 230.40 mist-net hours in the Protected Areas' two management zones, namely the Special Protection Zone (SPZ) and Tourism Zone (TZ). ILPLS has a high level of endemism at 33% (12 species), including nine Philippine endemics and three Mindanao Island endemics. We also recorded Gorsachius goisagi, a globally threatened species categorised by IUCN as Vulnerable. Species richness was higher in the SPZ than in the TZ (p = 0.012), whereas no significant differences were observed in the Shannon index values (p = 0.101) and mean capture rates (p = 0.378) between the two management zones. Species and feeding guild assemblages did not differ between the two management zones (p = 0.939) but varied between vertical strata (p = 0.001). Here, we show how this small, protected landscape harbours a comparatively diverse bird community, including restricted-range species and species with high conservation priority. This suggests that forest fragments, even of this size, are important habitats for bird conservation efforts and should not be undervalued. We recommend extending such studies to other fragments, especially those that are still not protected, to improve our biodiversity database, further our understanding of biodiversity and fragment dynamics, and make a case for the protection of other forest fragment habitats.