房総丘陵における鳥類群集の季節的変動

抄録

1. The author, having observed from April of 1967 to May of 1970 the seasonal changes of bird community in Ichihara City, Chiba Prefecture, which is the central part of the Boso Hills, observed birds of 12 orders, 26 families and 48 species.
2. In the Boso Hills, compared with other regions, the number of birds and of species of birds are not very large. Two reasons might be given for this. One is that this peninsula consists mainly of low hills with no higher mountains. Atagoyama, which is 405 meters high, for example, is the highest hill-top of this district. Consequently birds are very poorly distributed vertically. The other reason is that the town is far from coastlines and that it has few marshes and it is removed from the stop-over of migrant birds, particularly of water fowls.
3. This district is very important as a winter resort of birds, since the weather is very warm here even in winter, unlike the Central Mountain District. 11 species of winter birds were seen.
4. The birds in the hills are divided into three types: the farmland type represented by Emberiza cioides, the woodland type represented by Aegithalos caudatus, and the river type represented by Alcedo atthis.
5. On further investigation, it will be known that there are many more birds in the Boso Hills. Three years is too short to observe the behavior of birds, especially of winter birds.
6. By transect method, the author observed in Tsurumai, Ichihara City, the seasonal changes of the population density of birds in the area of 400m. by 500m., the result of which is classified by species.
7. On June 17, 1969 I took a census of birds in Tsurumai, and it was found out that 16 species of bird could be seen between four and six in the morning, 11 species between six and seven in the evening, and five to seven species in the daytime.
8. The investigation on the territory of Lanius bucephalus bucephalus and the distribution of Milvus migrans lineatus is reported in this article.