Another pair of Great Crested Grebes has hatched at least one chick -- there may be more but this is the only one whose little stripy head I could see poking out of his father's wings.

This is the pair from the northwest corner of the Serpentine island, and the adult has adopted this crouching posture because the is defying one of the pair from the northeast corner, who also have chicks. The invisible frontier between their territories is halfway along the landward side of the island.

Other grebe frontiers are easier to see. In this case the grebes on the right of the line of posts are defending their territory against invasion from the left.

One of the wire baskets full of twigs, teeming with small fish, is on the right of this picture; a precious resource to be defended. It doesn't matter, or course, that the basket contains enough fish to feed every grebe on the lake.

The female Mute Swan nesting below the parapet of the Italian Garden was sitting with her wings spread out, as if guarding something underneath them.

It looked very much as if her eggs had started to hatch. I waited for some time to see if she would move and give us a sight of what was going on, but she wouldn't, so I am just speculating here. Will keep a close eye on developments.

Again, there were hundreds of Swifts over the Serpentine, with a good number of House Martins at the east end near their nests in the Kuwaiti Embassy. Here a Swift zoom over the head of a Coot.

Its tail is fully deployed in executing a tight turn. When the bird is going straight ahead its tail is folded down to a neat little V to reduce drag, and plays almost no aerodynamic role at all. This is something that aircraft designers can only envy.