Dave Dawson’s natural history notes for 16th June 2017:-

The 90 Canada Geese and 90 Greylags were leaving the grasslands for the lake in the early morning. The Canada Goose number reflects both the slow increase in numbers over the last 30 years and the seasonal pattern: in June they move back from scattered breeding sites across a wide area of SW London to moult in the park. Greylags first arrived in 2000, and they increased up until 2014. They too have peak numbers in June, as do Egyptian Geese. The Egyptians seem to have stabilised at around 50 birds. In contrast to the Geese, about half of our Great-crested Grebes leave the lake in late Spring and their numbers have been declining since the turn of the millennium, and this is the first June that I failed to see any on the lake. Perhaps the grebe that died tangled in fishing line in late April hasn’t been replaced? The 23 Coots equalled the long term average number for June, confirming that this waterweed feeder has declined to normal numbers. In contrast, the other waterweed feeder, the Mute Swan, stays up at 30, well above the long-term average, if less than in the previous two years. There were many Swifts hawking insects over the lake and park, which were very difficult to count, but perhaps 100 birds. This equals the previous peak estimate, in June 2011. We have seen a long-term increase in Swift numbers here, contrary to the national picture where Swift numbers have halved over the last 20 years. In contrast, we used to average some 40 House Martins in summer over the lake in the late 80s and early 90s, but now the average is zero! Most other bird species are quiet at this time of year. Robins are busy rearing young, so June is their quietest month, but Wrens sing right through the spring and summer. The brook is looking good, with Hemlock Water-dropwort and Watercress in flower, and Hairy Willowherb about to flower. An odd record was a single tomato plant growing by the upper bridge. The lower brook has been invaded by some Love-in-the-mist from the adjacent “Wildflower Meadow” plot and also has some Water Bent, a species that is a recent arrival in London and spreading rapidly. The hedgerows and woodland edges were studded with the white trumpet flowers of the hybrid hedge bindweed and there’s a clump of Ox-eye Daisies by the northern hedgerow. Brambles were in flower. Novel this year is a clump of Bird’s-foot Trefoil around the base of a willow on the dam. The Glade has a good show of flowers, including those added for quick colour: Poppies, Mallow, Hedge Woundwort, Corncockle, Corn Camomile and Corn Marigold. Doing their own thing are Hogweed and Prickly Oxtoungue. The “Wildflower meadow” plots out in the short grass are growing, but with few flowers as yet. Another patch left to grow for daffodils by the southern hedge has allowed a remarkable stand of Meadow Barley to show. Very likely it will be sacrificed soon! The fumitory in the raised bed by the Wimbledon Park entrance is fruiting and dying back. The water of the lake is remarkably clear and this year the predominant waterweed is Lesser pondweed, a change from previous years and perhaps a sign of marginally better water quality.