Birdwatchers from the Wild Bird Club of the Philippines separate birding trips to the HINP on 19 June 2006 and 19 July 2006 have identified a total of 57 bird species. Aside from bird species, there are also mammals and reptiles that were identified. Considering the smallness of most of the islands that comprised the Hundred Islands National Park and the harsh environment that the coralline substrate of the islands provides, the species assemblage encountered is surprising.
While comparatively depauparate in terms of the number of species (which is to be expected in islands), this assemblage represents a unique sample of wildlife that had managed to and continue to survive in such harsh environments. If the estimated geological age of Hundred Islands is correct, which is around 2 million years old, then the wildlife assemblage represents a snapshot of evolution and adaptation that had taken place.
Fifty-seven (Terrestrial Vertebrates Present in the HINP By Description) species of birds were detected during a recent survey, comprised of eight (8) endemic species, one 1 near-endemic species, 36 resident species and 12 migrant species. Two of these bird species, the Philippine Duck Anas luzonica and the Java Sparrow Lonchura oryzivora were classified as Vulnerable under the Red List of Threatened Species by the International Union for the Conservation of Nature and Natural Resources (IUCN, 2003).
The eight endemic species observed in the islands were: Philippine Duck Anas luzonica, White-eared Brown-Dove Phapitreron leucotis, Philippine Hawk-Cuckoo Cuculus pectoralis, Philippine Coucal Centropus viridis, Philippine Bulbul Ixos philippinus, Elegant Tit Parus elegans, Lemon-throated Leaf-Warbler Phylloscopus cebuensis, and Grey-backed Tailorbird Orthotomus derbianus. Except for the Philippine Duck Anas luzonica, which was found in an extensive wetland in Brgy. Pandan, all of the endemic species were found within forests found in the islands. The Lowland White-Eye Zosterops meyeni, is considered a near-endemic species, as it could also be found in a very restricted range in Taiwan.
The area with the most number of species was the Pandan- Camantiles Island Wetlands followed by Century, Governor and Monkey islands. Apart from data gathered from the transect walks, the bird list for Governor Island was supplemented by capture data from mist-nets. The species list for the outlying islands in the north of the Park as well as the mudflats in front of the wharf was lumped together as most of the smaller islands only had a handful of birds detected during the bird search conducted aboard a boat. Most of these small islands were also made inaccessible by sharp rocks jutting out along its edges.