It has been raining almost non-stop since last night, and the area where the Olympic grandstand was is now a small lake. As usual, it is full of Black-Headed Gulls, which flock to flooded areas, probably looking for insects and other small creatures which have floated out of the grass.

On the impervious London clay any area of flat ground will flood quickly. More remarkably, there are also floods on sloping land, for example on the Parade Ground at the east end of the park. Both these areas seem more prone to flooding than before, possibly because the crowds have compacted the soil. The floor of the Serpentine is made of clay which has been deliberately trampled to make it waterproof -- this is called 'puddled' clay. In the 18th century when the Serpentine and the early British canals were constructed, builders would call out the entire population of neighbouring villages to stamp on the clay for a few pence a day.

This Black-Headed Gull looks much like any other, but it has a ring, EY09813.

The ring allows you to see that it always perches in the same place at the Vista, preferably on the same post. It was only ringed this January, so does not have much known history, but its deep red beak and legs show that it is several years old. Another ringed gull, EP24143, which favours a post to the left of this one, was ringed in Kensington Gardens in December 2002 and has been seen, always in Kensington Gardens, in the winters of 2005/6, 20006/7, 2010/11 and 2011/12, which shows these gulls' fidelity to their wintering grounds.

The rain had driven the male Tawny Owl into his hollow tree, but his mate was sitting on her usual balcony, on the downwind side of the tree and sheltered from the rain by an overhang.

The Little Grebes on the Long Water have expanded their fishing grounds up to the bridge. In previous years they have sometimes gone the whole way to the Serpentine island, and you could see them briskly paddling along the open lake shore to reach it, looking very small and exposed but their ability to dive in hundredths of a second saves them from harm.