Two Reed Warblers were singing loudly, one in the reed bed below the Diana fountain, the other on the west side of the Long Water. Here is a superb picture by Paul Sawford of the first one, taken yesterday.

Anyone who has ever tried to photograph a Reed Warbler will understand the patience, speed and sheer luck required to catch one of these maddeningly invisible birds, let alone get a perfect shot unobscured by reeds.

The two Common Terns remain on the Long Water. The male is bringing the female fish so often that even she sometimes refuses them, giving him a chance to eat his catch himself. Today she sat on the fallen horse chestnut tree for a while. Here a fish changes beaks, along with a strand of the hair algae that have grown in the lake during the recent warm days.

She spat out the algae when she had swallowed the fish. Terns don't like salad with their meals.

The two young Great Crested Grebes from the east end of the Serpentine island were out on the open water near the Bluebird Boats jetty, being fed by their parents.

One of them was offered a crayfish too large to swallow, which its father eventually ate. The young birds are already diving for a few seconds to see where their parents are, so they can move into a good place to take the next fish before the other chick gets there. They can already swim underwater with great speed, and are calling so loudly that you can hear them from the other side of the lake.

The young Pied Wagtails are already hunting for themselves. This one has just caught a grub on the shore near the Lido.

The Swifts are back, not surprisingly as the air above the lake is thronged with insects. There were about 30 of them, and about 20 House Martins from the colony in the Knightsbridge embassies.