Human-Altered Tree-Based Habitats and Their Value in Conserving Bird and Bat Diversity in Northeast Luzon, The Philippines - Smallholder Tree Growing for Rural Development and Environmental Services - page 338

Photo 16.1 A Gmelina arborea forest plantation surrounded by shrub-land in the foothills of the
Sierra Madre, the Philippines (©Van Weerd)
adjacent to village homegardens and Gmelina forest plantations were selected for
surveys to make a direct comparison of species richness between habitat types pos-
sible. Pure cultivated areas were not included in this study as they represent very
specific and changeable habitats, i.e., cornfields are expected to vary greatly in their
suitability as a habitat for birds depending on growing season.
16.2.3 SurveyMethods
The exact area of surveyed Gmelina forests could be determined as these were
confined, unconnected habitat islands within a landscape of different habitat types.
However, the area of surveyed homegardens and shrub-land could not be meaning-
fully determined as these habitats consisted of contiguous and interconnected land
use types in and around villages and along roads. Both birds and bats were therefore
surveyed using methods that enabled the calculation of relative measures of species
richness and densities which could be used further in statistical procedures.
16.2.3.1 Birds
Within the three habitat types combined, a total of 118 point counts were conducted
between 4 May and 25 July 2005 at well-spaced locations always more than 200 m
apart (Table 16.2). Point counts lasted 10 minutes each, started after a several