The most remarkable sight of the day was not of a bird. The first Holly Blue butterfly I've seen this year was flying around the terrace of the Lido restaurant, and settled on the arm of a man who was eating at one of the tables. It stayed there for almost a minute.

Another sighting: yesterday the first House Martins were reported flying over the Serpentine. I went to see if any had arrived at their nest sites on the Kuwaiti Embassy: not yet. They will need a bit of rain before they can nest, so they can have some mud to repair last year's nests.

The behaviour of the Grey Herons in the nest on the island is puzzling. They are usually together on the nest, and one of them is looking down into it.

This is the behaviour you would expect if they had recently hatched chicks. But they don't seem to have had time to produce these since they reoccupied the nest. It is possible that a heron was sitting on eggs very low in the nest and I didn't notice it, but this seems unlikely, as the sides of the nest are not veru high and usually you can see the back of a sitting bird. Anyway, we just have to wait and see.

There's another Coots' nest on the net at the east end of the Lido, this time built on the outside of the net as there is no hole for the Coots to get through. This at least protects it from the Grey Heron.

Yet another nest in an impossible place, on the edge of the Lido restaurant terrace.

The nest built directly on the bottom of the lake still doesn't have any eggs in it. The whole structure trembles when the Coot preens.

Nor, it seems, does the Moorhens' nest on the rock in the Dell. The pair here have bred successfully every year for some time.

Everything is fine on the Great Crested Grebes' nest on the island, where we know there are four eggs.

A Mandarin drake shone brilliantly as he turned around at the Vista.

The Mandarin drakes and the Coots at Peter Pan were each having private disputes. Perhaps the Mandarins set the Coots off, as the slightest disturbance can start these irritable birds fighting.

At the Mandarins' nest in the plane tree near the Albert Memorial, two drakes were on guard.

The moment of peace didn't last, and they started chasing each other.

There was no sign of the Little Owls in the next tree, nor of the ones at the leaf yard, in spite of the warm sunshine. With luck this means that both females are nesting.

Two of the Canada--Greylag hybrid geese were dozing on the edge of the Serpentine.

A Robin beside the Long Water came out to be fed. This is one of a pair, and probably the other is nesting in the brambles.

A Long-Tailed Tit in the Dell was feeling the heat, and panting to cool itself.

We haven't seen much of the Jays recently, but today one came out to be fed.

A Jackdaw on a branch expertly shelled a peanut.