Reedbeds are dominated by one plant, the common reed, but this habitat in turn supports a range of specialist wildlife.
Filsham Nature Reserve also contains many flower-rich margins, reed-fen, and areas of scrub and tussocky vegetation. The bird populations are particularly important and during the breeding season, the reedbed is full of the songs of reed and sedge warbler along with Cetti’s warbler, reed bunting and cuckoo. Bearded tit also breeds, though only in small numbers. The scrub around the edge of the reserve is important for a range of species including bullfinch, song thrush, dunnock and whitethroat. The reedbed, and indeed the whole of the valley, is an important migration route with many exciting birds seen in the spring or autumn including purple heron, bee-eater, wood warbler and red-backed shrike. Hobbies can often be seen hunting insects at the back of the pond when they first arrive in the country before heading to their breeding grounds. In the winter you might see a bittern, marsh harrier or short-eared owl hunting over the reedbed, and Cetti’s warbler and water rail are often very vocal. Snipe like to feed in the damp short areas, often where reed cutting has taken place.
While reedbed is the dominant habitat at Filsham, reed-fen is also present. This habitat is much more botanically diverse than the pure stands of reed and is probably the rarest habitat on site. Here, we cut or graze in the summer, or a combination of both, which reduces the vigour of the reed and allows other plants to flourish such as blunt-flowered rush, ragged robin, water mint and marsh pennywort. There are also swamp communities present on site, often found where invading willow has recently been removed. Species such as red sweet-grass, reedmace and branched bur-reed all thrive here. There are also pockets of other interesting plants around the site including areas of common meadow-rue and corky-fruited water-dropwort.
Over 1000 species of invertebrate have been recorded on the reserve, and there is a very distinctive moth fauna associated with reedbeds. Filsham has been well surveyed over the years and has some rarities which is indicative of good quality wetland habitat. The larvae of some of these moths feed on the reed itself, for example reed dagger, flame wainscot and the recently discovered Brachmia inornatella. All are dependent on good quality reed being present. Other moths found at Filsham include Webb’s wainscot which depends on yellow iris and bulrush, dotted fan-foot and Nascia cilialis on rushes and sedges. Acleris lorquiniana, a purple loosestrife feeder, is only known at two sites in Sussex. Filsham Reedbed also supports some specialist beetles such as the reed beetle Donacia clavipes which favours the areas of pure reed. Another, Stenus palustris, is also found at Filsham Reedbed, the only place to find it in Sussex.
As you walk around the paths on the reedbed, there are many plants important to a range of insects. Hemlock water-dropwort supports the moth Depressaria daucella, the larvae of which can be found on its flowers in June. Yellow loosestrife can be common on the reserve too and where it is present, Macropis europaea sometimes known as the yellow faced bee, can often be found. Around the edge of the reedbed, where it turns to grass and scrub, is where small mammals make their home. Harvest mice nests, tennis ball size tightly woven balls of reed, can sometime be seen.
The reedbed needs constant management to keep it in good condition. Willow always wants to invade the reedbed and would quickly take over if left alone. Leaf litter from the reeds themselves can build up causing the reedbed to dry out, resulting in short and weak reed stems, not much good to build a nest in. Therefore, during the winter much time is spent with staff and volunteers cutting back willow scrub and cutting the reed on a rotation of about nine years. This creates open wet areas within the reedbed, perfect for wintering snipe and refuge areas are always left within the cut areas for the benefit of overwintering invertebrates. Internal sluices and bunds means we can control the water levels within the reedbed, however the whole of the valley often floods in the winter preventing access to the reedbed for management works.The ditches and pond also need management to prevent the reed taking over and so these are cleared on rotation too, maintaining areas of open water important for dragonflies and birds alike. We often find that once a ditch has been cleared insectivorous bladderwort appears for a few years. The ditches also have a rich flora with special plants like water-violet present. The open water is important for birds but also for dragonflies and 20 species have been recorded on the reserve including hairy dragonfly, variable damselfly and ruddy darter.