Sunday, 8 August 2010


Top - the King George V Reservoir on a standard day, lower - the King George V Reservoir on a good day.

I rather like moulting Tufted Ducks. Perhaps it’s because there’s precious little else to look at on the rezzers at this time of year. Or perhaps it’s the challenge of pulling out something unusual amongst the scruffy legions as you scan through them one by one. Perhaps a Ring-necked Duck, or a Scaup, or even a Lesser. I’ve managed a Scaup or two and a couple of Fuggy Ducks over the years but that’s about it, as far as I can remember. Anyway it’s that time of year again, so my third count of the birds on the King George and Girling Reservoirs in the last fortnight turned up 925. The ‘unusuals’ were represented by 3 Goldeneye and the supporting cast by 24 Black-necked Grebes and a handful of Common Sandpipers.

In recent years, the August moulting flocks usually form the peak annual count of Tufted Duck in the Lee Valley, with an average peak of around 3,000 birds. The previous mid-winter peak now seems less pronounced. The moulting hordes on the reservoirs (including Walthamstow) make up over two-thirds of this total and are nearly all drakes. It appears that the drakes that arrive here to moult are from the eastern parts of the European range, principally Russia and eastern Scandinavia. Less than 10% of females undertake a moult migration. The sex ratio of 80%+ drakes is maintained on the reservoirs through the winter although the numbers drop, while the ratio on the gravel pits seems to be about 60% drakes. Do the deeper diving drakes prefer the deeper reservoirs? Do some of the moulting drakes stay for the winter or are they replaced by others? The moulting period is characterised by very stable flocks but they become highly mobile as the moult is completed. How much of the food resource have they depleted during this period? Is this why the Girling is crap during the winter? Something to ponder whilst checking for that Lesser.

No comments: