STRICTLY NO DOGS. Please keep to the Trail and especially avoid walking down to the shore since this will scare the birds which other people are trying to watch. We aim to create an undisturbed wildlife reserve area beyond this part, so please do NOT attempt to join the Trail from any other direction. Note also that the Hollow Brook car park is for anglers only.

REMEMBER TO KEEP QUIET AND TO KEEP YOUR EYES AND EARS OPEN, ESPECIALLY TO ANY MOVEMENT IN THE REEDBEDS AND WOODLAND. THE LESS DISTURBANCE YOU CAUSE THE MORE WILDLIFE YOU WILL SEE.

THE BITTERN TRAIL - A GUIDE

THE FOOTBRIDGE The changing level of water under the footbridge thought the year results from the use of Chew Valley Reservoir to store winter run-off and maintain drinking water supplies through dry summer months. The highest levels are usually seen in March and the lowest in September. This regime has a very strong influence on the plants and insects which inhabit the margins of the Lake, Willows, reeds and Amphibious Bistort not only withstand inundation, but also survive long dry periods so, not surprisingly, these are the most successful marginal plants at Chew. Others, such as the yellow-flowered Silverweed the white Scentless Mayweed, and the delicate star-shaped Water Chickweed, which is also white, are quick to invade the exposed lake bed. When crossing the bridge look, too, for a flash of blue - Hollow Brook is a favourite hunting area for Kingfishers. Follow the arrows through the car park to a meadow.

THE MEADOW This sheltered narrow grassland is ideal for seeing small birds and insects. You may see a party of busy Long-tailed Tits making their twittering passage from tree to tree as they search for aphids. In the winter Siskins frequently feed on the seeds of alder. Butterflies like Brimstone, Common Blue and Comma can be seen in this meadow and in late summer Small Tortoiseshells are common.

SYCAMORE WOOD This woodland is mixed Sycamore, Norway Maple, Willow and Alder plantation, and is being managed by selective thinning. This will improve the woodland's structure and improve its wildlife value. As you begin to leave the dense canopy above look out for fragrant Meadowsweet, blue Water Forget-me-not and Water Mint growing beside the small drainage ditches.

OPEN GLADE. This area is mown only infrequently and supports a variety of moisture-loving taller herbs, reeds, rushes and grasses. Look out for bright blue flowers of Meadow Cranesbill, the yellow and blue of various Vetches and the bright colour of Purple Loosestrife. The taller grasses here also attract butterflies, while dragonflies including the Ruddy Sympetrum may be seen hawking for insect prey. The area between the Trail and the Lake has been massively invaded by Willows, White Willow is tall and tree-like with long leaves, while the Grey Willow is more shrub-like, with oval-shaped, olive-coloured leaves. In other places you can see slender Withies with their very long narrow leaves. Nearer the Lake the willow roots are exposed when the Lake is low, their stilted appearance giving a distinct impression of mangrove swamp.

THE BIRD HIDE From the bird hide you may see a wide range of birds, Canada Geese, Coots and Heron are present all year, but the greatest number of duck are usually seen in early winter. Typical duck species to be seen include Mallard, Pochard, Teal, Tufted Duck, Shoveler and Wigeon, with less common species including Goosander, Shelduck, Pintail, Scaup, Long-tailed Duck, Garganey, Smew and Red-crested Pochard. The stiff-tailed Ruddy Ducks are of interest since they are a feral population, established from birds which escaped from Slimbridge. Late in the summer, you may also catch a glimpse of a Cormorant sitting on a favourite tree-stump with wings held out to dry as though posing for some heraldic design. They find rich pickings from among the Roach, Rudd and Perch populations in the Lake, and can also take the occasional Trout. The bay is a good feeding area for waders, especially during their autumn passage. Lapwing are common, but also look out for Common Sandpiper, Greenshank, Snipe and Dunlin. Retrace your route beside the fence and cross over the bridge into the reedbeds.

REEDBEDS For 400m the trail runs between woodland or Dogwood scrub and reedbeds. Blocks of the reedbed may have been cut recently as part of a rolling programme to prevent further invasion by willow and bramble. Block cutting maintains a proportion of young reads and provides a contrast with the mature stands and thus increases habitat diversity. Apart from the familiar reedbed birds seen or heard on the Grebe Trail, this wilder, more extensive area of reeds may attract more unusual visitors. The small, fast-flying Hobby has been seen here hunting for Swifts, Swallows and Dragonflies. The bird most closely identified with reedbeds, the Bittern, is an occasional visitor to Chew. Look, too, at patches of damp earth along this part of the Trail. Roe Deer 'slots' are quite common, as are the hairy-toed prints of Fox. You may notice Willow saplings with areas of bark rubbed away - the result of a Roe buck thrashing his small antlers in the build-up to the late July rut.

OLD HEDGE AND DITCH The Trail turns and doubles back in a northerly direction at an old ditch with sandy banks much dug by Rabbits. Indeed, much of the return walk follows good Rabbit country with a high hedge, low bushes for cover, a sandy bank in which to dig holes and plenty of grass for grazing. In autumn the bushes bear red haw berries and blue-black sloes. The hazels with their nuts and the Oaks with their acorns are attractive to Grey Squirrels. Small passages through tufts of grass mark the runways of Mice and Voles. Both Voles and Rabbits have seriously damaged the bases of the Norway Maple and Sycamores in the plantations. As you follow the Trail along the back of the Dogweed shrubbery and the plantation have a look at some of the small Oak treas: one or two may have large bud-like growths on their acorns. These are Knopper Galls, a relatively recent introduction to the area caused by the grub of an insect. The familiar round Oak Apples are also galls - hard wood produced by the oak itself to surround the larva of an Ichneumon Wasp which feeds and grows inside the gall until it turns into an adult and eats its way out, leaving behind a characteristic round hole. Interestingly, other Ichneumon wasps parasite the oak apple grub itself and are in turn the host to another parasite. No wonder oak trees provide such a rich larder for insect-eating birds.

Bristol Water plc gratefully acknowledges the support of the Countryside Commission and the Nature Conservancy Council in the creation of the nature trail.