An afternoon visit with fog hanging low over the water provided the following species:-
Little Grebe (4), Great Crested Grebe (5), Great Cormorant (60), Little Egret (1), Grey Heron (5), Mute Swan (3), Greylag Goose (1), Canada Goose (2), Eurasian Wigeon (20), Gadwall (6), Common Teal (5), Hybrid Duck (1), Mallard (14), Northern Shoveler (2), Common Pochard (35), Tufted Duck (240), Common Goldeneye (3), Goosander (male on River Colne), Common Moorhen (13), Eurasian Coot (145), Northern Lapwing (40), Red Kite (1), Black-headed Gull (300), Common Gull (2), Herring Gull (4), Lesser Black-backed Gull (1), Great Black-backed Gull (6), Woodpigeon (7), Ring-necked Parakeet (1), Common Kingfisher (1), Green Woodpecker (1), Great Spotted Woodpecker (2), Grey Wagtail (2), Wren (6), Dunnock (4), European Robin (7), Common Blackbird (5), Song Thrush (1), Cetti’s Warbler (2), Common Chiffchaff (4), Siberian Chiffchaff (1), Goldcrest (9), Long-tailed Tit (17), Blue Tit (2), Great Tit (1), Eurasian Jay (1), Common Magpie (3), Western Jackdaw (5), Carrion Crow (6), European Goldfinch (11).
At the north end of the lake I discovered a Siberian Chiffchaff which was wearing a metal ring on its leg. It busily fed on flying insects from Crack Willows that overhang the River Colne. The plumage of the bird was much paler and more grey looking than the Common Chiffchaff that were also present. The River Colne at this particular location acts as the county boundary and so this bird can be added to both the London and Hertfordshire lists.
Siberian Chiffchaff Phylloscopus collybita tristis.
At the south end of the lake a Cetti's Warbler gave fantastic views as it fed among an area of dogwood that overhangs the river bank. This area is fantastic for insectivores with Goldcrest, Common Chiffchaff and Tits all observed catching flying insects. This also happens to be where HS2 will eventually cross the River Colne so it's days, I'm very sad to say, are numbered.