Abstract
The spring migration flights of the Brown-eared Bulbul Hypsipetes amaurotis were observed on the shore of Lake Biwa at Hikone City, Shiga Prefecture, Japan, over thirty days between 12 April and 13 May, 2005. The relationship between migratory flight activity and weather conditions was investigated. A total of 142 flocks, consisting of 5,338 individuals, were observed during the study period. The maximum number of flocks (25) was recorded on 23 April and that of individuals (1,257) on 19 April. On fine and calm days, many migratory flocks were recorded, whereas few were evident on windy days. A negative correlation was detected between the number of migratory flocks and wind velocity. Moreover, many migratory flocks were observed in the morning, especially between 06 : 00 and 09 : 00. In contrast, the flights of resident birds were observed even on windy days and in the afternoon. The flight direction for migratory birds was concentrated toward the northeast, a direction parallel to the coastline of Lake Biwa, and migratory flocks may utilise the coastline of Lake Biwa as landmark.
