PLANTS

Over 85% of wetland species growing in ponds occur in the drawdown zone, and many are restricted to this area. Examples of rarities to be found in drawdown areas include plants such as Six-stamened Waterwort, Thread Rush, Mudwort, Pillwort and Shoreweed. A number of rare bryophytes are also adapted for colonizing bare mud, and hence benefit from drawdown in reservoirs and other water bodies.

INVERTEBRATES

A number of macroinvertebrates appear to be adapted to fluctuating water levels and can cope with or even benefit from regular drawdown. Diverse drawdown habitats provide conditions that invertebrates can use during the wet or dry phases in synchronisation with their life cycle. The aquatic invertebrate communities are often characterised by mobile groups such as microcrustaceans, beetles and waterboatmen that are able to respond to changes in water level by migrating into new littoral regions. An alternative adaptation for species with low mobility and resistance to desiccation such as mussels and snails is to become dormant, sealing off the shell opening to resist drying out. 

BIRDS

Drawdown zones can provide important breeding and migratory habitat for a range of bird life throughout the year. Drawdown in spring attracts passage waders such as Golden Plover, Redshank, Oystercatcher and Common Sandpiper to feed on the ready source of invertebrates present in sediments, exposed shallows and bare ground. The same conditions in summer make good duckling rearing habitat. Waders can again make use of the large drawdowns common in the late summer and autumn on their return passage. Reflooding over the winter then releases drowned invertebrates and the copious seed produced by plants during the summer drawdown, providing food for wildfowl such as Teal and Shoveler.