The solitary female Mute Swan who has been in the Italian Garden pond for months seems to have found love. The male arrived several days ago, but it was not until yesterday that I saw them arching their necks and dipping their heads in synchrony -- a swan's courtship display. They were courting again today, and evidently they have bonded.

Of course it is entirely the wrong time of year, but swans mate for life and they have plenty of time. It remains to be seen whether they will venture on to the hotly contested main lake where a junior pair will be most unlikely to win a nest site. They are both only in their second year, as you can see from the rather dull orange of their bills.

A young Blackbird was eating rowan berries on one of the trees on Buck Hill.

But I have still not seen much activity on the four heavily fruited trees at the top of the hill near the gate, or any sign of the arrival of the migrant Mistle Thrushes that eat them.

Mateusz Kociński, who works at Bluebird Boats, has been keeping an eye on the crayfish in the lake. The net at the boathouse is now capturing quite large signal crayfish, as well as the Turkish crayfish that were here earlier. Here are two of his pictures, showing the reddish colour  of the signal crayfish -- the first one is a very dark specimen ...

... and the bright red underside of its claws, which it waves around in the display that gave the creature its name.

Compare this picture of a Turkish crayfish from the lake, showing its lighter build and greenish colour. Both species have been introduced into British waters in recent years and are steadily wiping out the native crayfish. In the Serpentine, it seems probable that they were introduced deliberately by someone who wanted to catch and sell them. In fact they may have been put in a second time, after all or nearly all of the crayfish died in 2008 when algicide ran into the lake from the Diana fountain.

Not far from the boathouse, the Great Crested Grebes are feeding small crayfish to their chicks.