I had a go at shooting a video of them today (I apologise for the camera work - I did my best!)
I've slowed down part of the video (as they are so fast), then it goes back to full speed in the second half. Watch out for the poor Blackbird that bravely tried to grab some chicken at the start of the video.
This second video shows the kites chasing each other mid-air and really shows how agile they are. Again the first part is slowed down (hence the funny voices), then it goes to full speed.
What a treat for Father's Day!