They come with summer, they go with summer

It's a real privilege to witness natural events close up.  I'm really blessed to have five house martin nests on my house, four on the west wall and one on the east (as well as the swifts on the north).  They seem to have had a good year, with chirpings from young almost continuously and even still now.

But last week there was a pre-migration gathering of what looked like hundreds of house martins from I can't imagine how far afield, wheeling and calling round and round, flying right up to and even clipping my windows with their wings.  Here's the video.  As I say, 'I've never seen anything like it.'  Do click on it and enlarge to view - but my apologies, one day I'll remember to video in landscape.