Significant departure of Swallow form 8am onwards, a few House Martin and Sand Martin in the passage, birds passing down river in their thousands. Very rough estimate 9000 an hour (difficult to put a figure to) at one point like a swarm about 900-1200 birds low at tree top height, but a large number passing very high presumably better winds/thermals at height. When you consider I have just a snap shot of this migration, it makes me wonder of what the bigger picture must be.
