The Taiwan Breeding Bird Survey Data

BBS Taiwan applied a stratified random sampling scheme for an initial set of 450 sampling sites aimed at covering 5% of the c.f. 36,000 km2 area of the Taiwan Island. Nighty-one stratums, defined by 41 eco-regions (Su 1992) combined with three different elevation zones (0-1,000m, 1,000-2,500m, 2,500-4,000m) where used in this progress. An additional “customized” set of samplings sites were selected manually by surveyors at locations where no pre-selected sites covers. To date, all types of sampling sites now reach approximately a number of 750 sites. All sampling sites were available to be adopted by volunteered surveyors each year, while encouraging the same surveyor to adopt the same sampling site as long as possible. Each sampling sites were surveyed twice a year, which, in combination with the 6 – 10 survey points per site, gives each site a minimum sampling effort of 12 times. The above sampling effort ensures the likelihood of detecting 80% of species present and keeping the coefficient of variance below 20 % in the breeding season within each site on Taiwan (Ding 1993, Shiu and Lee 2003). Surveys are performed within the breeding season between March and June, with sites at higher elevations surveyed in a later sequence. Surveys are conducted within four hours of sunrise on each day. Point-count method (Bibby et al. 2000) with a 6-minute stop time were conducted on each survey point, ensuring the effort to detect a minimum of 80% of the species at each site (Ding 1993, Shiu and Lee 2003). We record every bird individuals detected, regardless of migratory status and either sighted or heard. For each bird record, the period of detection time (0-3 minutes, 3-6 minutes, supplementary which are records beyond the 6-minute stop time), horizontal distance to the observer (0-25m, 25-100m, >100m., flyover), and formation of flock with more than five individuals were recorded. For each survey point, the main-habitat, sub-habitat, presence of water-bodies, weather condition, starting time were recorded. Habitat were classified by surveyors on field.