Shin-Ichi SEKI
Ornithological Science 4 (2), 117-128, (1 November 2005) https://doi.org/10.2326/osj.4.117
KEYWORDS: bird community, Dietary and foraging guilds, seasonal change, Typhoon disturbance, Warm temperate forest
The effects of a severe typhoon (9918 Bart) on a bird community in a warm temperate forest, southern Japan, in 1999, were investigated. The total abundance and number of species showed clear seasonality in normal years, and were higher during winter mostly due to the influx of winter visitor species. The composition of dietary and foraging guilds also changed among seasons. Among the dietary guilds, frugivores/granivores and omnivores increased in winter, whereas insectivores decreased in winter. As for the foraging guilds, forest interior- or edge-dependent species increased in winter, whereas generalists remained constant. Therefore, I examined the effects of typhoon 9918 Bart in winter and in summer, comparing the data sets from three years before and two years after its passage. In the first winter after the typhoon, the abundance of birds was significantly lower than in all three control years, however it recovered to the same level as the control years in the second winter. In contrast, in both the first and second summer after the typhoon, bird abundance was significantly higher than in the control years. The effects of the typhoon also differed among the dietary and foraging guilds. The winter dominant frugivores/granivores were fewer in the first winter leading to a decrease in total bird abundance in that season, whereas the increase in omnivores and insectivores resulted in the increased total bird abundance in summer. The reduction in forest interior-dependent species led to the lower total abundance in winter, and the increase in forest edge-dependent species may have led to the increase in total bird abundance both in winter and in summer. These different responses among different foraging and dietary guilds affected total bird abundance in concert. The disturbance event (typhoon) appeared to cause opposing effects on total bird abundance in winter and in summer.