Abstract
Flocking of Delichon urbica around a big abandoned chimney in Miyako City, Iwate, was observed during 1959-1961. There were no distinct correlations with weather, food, air current or breeding conditions, other than the fact that they gathered on calm fine mornings (with wind velocity less than 3), and increased in number from July to September and October. They seemed only enjoy-a sociable flocking around a distinct object on the way of migration.
