Population density, home range, and habitat use of crested serpent-eagles (Spilornis cheela hoya) in Southern Taiwan: Using distance-based analysis and compositional analysis at different spatial scales

For many tropical raptors, studies of population density and habitat use are still lacking. We used radio-tracking to study population density, home-range size, and habitat use of the Formosan Crested Serpent-Eagle (Spilornis cheela hoya) in Kenting National Park, southern Taiwan, during 1995-1997 and 1998-2007. Over two years, we documented a minimum population density of 2.69 individuals/km², which is one of the highest ever reported. Home ranges calculated using minimum convex polygons and 95% fixed kernel areas averaged 12.34 km² and 2.86 km² (n = 18), respectively. Core areas represented by the 50% fixed kernel areas averaged 0.41 km². We used distance-based analysis and compositional analysis to compare habitat use within the entire study area and the home ranges. Both methods indicated the overwhelming use (>90%) of somewhat degraded and semi-open mixed forests, followed by the use of Acacia confusa forests and grasslands to a much lesser degree. Habitat use was nonrandom both within the study area and the home range, as mixed forests covered only 24.4% of the study area. Many perch sites were near the primary monsoon forest, which was, however, almost never used for hunting. As many other species of serpent-eagles are threatened by habitat loss and human persecution, our study provides valuable information for their future monitoring and management.