環境

Recently, in the mountainous watersheds of the Tama River, large scale deforestation is being conducted by the Tokyo Metropolitan Government for reasons such as pollen-based allergy prevention. As a result, much open space is created and this is seen to have great impact on various living things. In this study, we conducted field studies of the grey nightjar (Caprimulgus indicus) and grey-faced buzzard (Butastur indicus) in 2015 and 2016 to find out the relationship between their inhabitation and deforested areas.
For the grey nightjar, inhabitation studies were conducted at 34 deforested areas as well as at quarries in the river beds, that is open space similar to the deforested area. We also did a study in forests without deforested areas. While we found that grey nightjar inhabited quarries at the highest frequency, we also confirmed their inhabitation at the 23 deforested areas that we studied, suggesting that they are also important habitats for grey nightjar. We further found after analyzing their inhabitation environment in the deforested areas that they tend to inhabit the areas when the deforested area exceeded 4.3ha.
For the grey-faced buzzard, we studied 24 deforested areas and 5 areas of open grasslands, and confirmed their inhabitation at 4 and 3 areas, respectively. When compared to the study results conducted in Tokyo metropolitan areas in the 1990s, this may imply that their habitats are being restored. We found their two nesting grounds, and found lizards and grass hoppers in two nests to feed the baby birds. These prey items are the ones commonly found in deforested areas. The ratio of these prey items to all feed found in the nests, however, differed among the two nests, which suggests that depending on the surrounding environment, there are differences in the frequency of using the deforested areas as their feeding spots. 

Nozomu Mitarai
Oki Koji