On a mild, sunny mid-September afternoon I'm walking towards Pen ponds in Richmond park.

Small heath and small copper butterflies feed on ragwort; reed buntings call and flit among fading bracken at the water's edge when from behind me, flying fast, comes what at first glance appears to be a kestrel. But this is no kestrel, having darker plumage and its flight is too dashing and jinking as it arrows towards a distant tree belt.

Suddenly the bird is back, flying towards the pond and I realize that it is in fact a hobby. A spectacular small falcon with sickle-shaped wings, the hobby somewhat resembles and flies rather like an outsize swift and indeed, its main prey consists of swifts, swallows and dragonflies, all skilfully caught on the wing.

But the swifts have long gone and swallows are in the process of leaving so the hobby is after dragonflies of which there are plenty still around. Soaring, diving, twisting this way and that at breathtaking speed, it performs for only about three minutes before swooping off into the distance over the heather.

For many years hobbies have nested not far away as the crow flies and they love the park's wide open spaces above which they perfect their aerial hunting skills and are exciting to watch.

This is probably the last time I will see them this year as they will shortly begin their 2,500 mile flight to sub-Saharan Africa, returning in late April or May.