Coate Water Site of Special Scientific Interest
National Grid Reference: SU 188820
Area: 51.1 ha [126.4 acres]
Description and Reasons for Notification
Coate Water has a diverse breeding bird population associated with two lakes and adjacent semi-natural vegetation. The site is one of the most important in Wiltshire for breeding reed warblers and great-crested grebes, it also
supports a wide range of dragonflies and damselflies and has botanical interest.
The larger lake was constructed as a canal feeder reservoir but became obsolete in the 1840s and is now very popular with the public as a recreation area. Adjacent meadows were shallowly flooded in 1975 to produce
a second lake, now an actively managed nature reserve.
Semi-natural woodland around the older lake is largely dominated by ash (Fraxinus excelsior) and oak (Quercus robus) with abundant sallow (Salix spp) in the wettest parts. A variety of woodland herbs is present including
enchanter's nightshade (Circaea lutetiana), wood avens (Geum urbanum), dog's mercury (Mecurialis perennis) and wood sedge (Carex sylvatica). At the water's edge willow scrub gives way to a tall fen community dominated by common reed (Phragmites australis) with some reed sweet-grass (Glyceria maxima).
The margin of the newer lake already supports reed beds and other wetland vegetation including brown sedge (Carex disticha), slender tufted-sedge (C.acuta), creeping forget-me-not (Mysotis secunda) and the notable golden dock (Rumex maritimus). Surrounding this are a number of wet meadows and smaller areas of recently planted deciduous trees and shrubs. The meadows are dominated by grasses such as crested dog's-tail (Cynosurus critatus), creeping bent (Agrostis stolonifera) and meadow foxtail (Alopecurus pratensis) but large areas of sedges (Carex spp) and rushes (Juncus spp also occur. Field boundaries compromise thick old hedges with numerous mature oak and ash trees.
Breeding summer migrant birds which frequent the lakes include forty pairs of reed warbler and several pairs of sedge warbler. Mallard, moorhen, coot and great-crested grebe are common residents, the latter usually numbering
about seven nesting pairs. Reed bunting and Canada goose breed here annually and tufted duck does so in some years. Water rail has also recently bred.
Amongst the wide range of woodland birds are many summer visitors such as nightingale, blackcap and garden warbler. Resident species include marsh and willow tit in small numbers as well as larger populations of the commoner
tits and treecreeper. A pair of tawny owls is usually present and both great spotted and lesser spotted woodpeckers breed irregularly.
Coate Water is also important for wintering waterfowl, particularly teal, coot, great-crested grebe, Canada goose and mallard. Further species occur on passage in spring and autumn such as common sandpiper, common tern and
black tern. Birds using the lakes as a summer feeding ground, whilst breeding elsewhere, include swallow, house martin and occasionally hobby.
The site provides habitat for a variety of insects including an outstanding assemblage of dragonflies and damselflies which flourish along the shallow lake margins. Fifteen species have been recently recorded such as the
emperor dragonfly (Anax imperator), the four-spotted chaser (Libellula quadrimaculata) and four species of hawker (Aeshna spp). The red-eyed damselfly (Erythromma najas), which is of nationally restricted
distribution, is one of six species of damselfly to be found at Coate Water.