Tuesday 26 March 2013

Time for my end-of-the-month bird count. Usually when I do this in the last week of March almost all the Black-Headed Gulls have already left. But today I found 383 of them, nearly all now in full breeding plumage, hanging around ready to go but not gone yet.

A postscript to Andy Sunters's helpful comment on the entry for 24 March about the Black-Headed Gull playing with a stick. He has made a sequence of pictures of a gull playing the whole game of dropping a stick and then flying down to catch it in midair; well worth a look. Today on the lake, our gull was playing with a bigger stick but still dropping it in the water rather than catching it as it fell.

Some Shovellers are still here, though I only found 17 on the Long Water and two on the Round Pond.

There were several Pied Wagtails flitting round the edge of the Serpentine, hard to count as they whizz out of sight and you are not sure whether the next sighting is of the same bird. Here one perches in a tree, looking quite unlike the strongly patterened black and white bird you see when they are running around on the ground.

There was a small flock of Goldfinches flying around trees near Kensington Palace, hard to see clearly against the sky but instantly recognisable by their excited chattering.

More news about the shells of oriental Golden Clam (Cornicula fluminea) found in boats on the Serpentine -- see my entry for 3 March. It is now almost certain that this identification is right, and the London Invasive Species Initiative and the Environment Agency are concerned about the invasion. The species has already been found in the Thames at Twickenham and Ham. When very small, the clams can stick to the plumage of birds and thus be carried long distances. It is possible that they came over on gulls from Holland, for example, where these clams are already established. They have a harmful effect on fish, as small clams grow as a parasite in their gills. Colonies of clams have also caused trouble by blocking water filters. They are normally thought of as a species of warm climates, and have revealed unexpected powers of survival in cold conditions.


  1. Now I realise that these are the shells I found on the beach of the Thames somewhere in Central London, within the last few months (can't remember where for sure, probably somewhere near Southbank). But I suppose empty shells could just be washed down/up river by the tides.

  2. The ones in the Serpentine were found in boats, and must have been dropped by gulls. The same could happen on the river, so shells could turn up anywhere. I am guessing that the clams died of natural causes (cold weather?) and the shells gaped open, so that the gulls were able to extract the contents, after which they would have dropped the empty shell wherever they happened to be.