When the swallows come home to roost.

The Bangkok Christian Guesthouse is about two blocks from Silom Road which in one of Bkk's major streets. Some trees remain from the wooded area that it once was. It is the traditional roosting area for Bkk's large population of swallows. During the day the swallows disperse throughout the city chasing the insects on which they live.
Sun sets about 6pm year around and about 7pm the swallows come home to roost. However, they do not fly directly to their chosen tree but swoop and fly around for about an half hour. With thousands of swallows swooping overhead you can guess why many of the women walking on the sidewalk choose to hold their purse on their head. By the time the swallows settle in for the night the sidewalk is splashed white. In the morning the swallows fly off for the day and the street washers go to work.
Think Bkk's dirty? The streets and sidewalks are washed every morning!