Under the Ramsar Convention, a wetland is considered internationally important if it regularly holds at least 1% of the individuals in a population of one species or sub-species of waterbird and/or 20,000 or more waterbirds. Special Protection Areas (SPA’s) are also designated areas of international ornithological importance. In Sussex, Pagham, Chichester and Langstone Harbours, and the Arun Valley (Including Pulborough and Amberley) are both Ramsar sites and SPA’s. In addition, Pevensey levels is a designated Ramsar site, and Dungeness to Pett Levels is an SPA. A large number of the birds visiting these protected sites are seasonal migrants. Internationally important populations of lapwing, redshank, snipe, kingfisher and bewick swans and important overwintering populations of pintail, shoveler, teal, wigeon and other duck species are found in the Arun valley and at other sites.
There are over 50 Biodiversity Action Plan priority bird species in Sussex which require conservation action. Fifteen of these species are closely associated with wetlands. Common wetland bird species also support other local bird populations, such as reed warblers which are one of the main species predated by cuckoo’s.
Table shows some of the Priority wetland bird species occurring in Sussex
| Name | Name Habitat Requirements |
| marsh warbler Acrocephalus palustris | Tall-herb often dense vegetation and scattered scrub (including rosebay willowherb, nettle and hogweed) |
| bittern Botaurus stellaris | Wet reedbed and marshland |
| twite Carduelis flavirostris | Saltmarshes, and grazing marshes during winter, breeding on moorland |
| bewick’s swan | Extensive wetlands and pools with emergent vegetation, will also use arable land and pastures with short grassy swards or root crops |
| reed bunting Emberiza schoeniclus | Wetlands including reedbeds, tall rushes and wet grassland with good vegetation cover, gardens, farmland, hedgerows, ditches |
| herring gull Larus argentatus | Nests on cliff tops, saltmarsh, shingle, coastal grassland, urban roofs, winters on pasture, arable and urban recreational grassland |
| black-tailed godwit Limosa limosa | Saline lagoons and estuaries, breeding on grazing marsh and other wetland habitats |
| savi's warbler Locustella luscinioides | Extensive reedbed close to water |
| grasshopper warbler Locustella naevia | Scrub, thick grassland, reedbeds, forestry and gravel pits |
| yellow wagtail | Wet meadows and pastures with ponds or ditches and a mosaic of short swards and tussocks |
| curlew Numenius arquata | Reedbeds, estuaries, damp grassland, heathland, mosaic of tall vegetation for nesting with short vegetation and open habitats for feeding |
| grey partridge Perdix perdix | Farmland, rush pastures, moors, mosaics of bare ground and cover, hedgerows, uncultivated margins |
| willow tit Poecile montanus | Damper habitats such as bogs, marshes and wet woodland. Almost extinct in Sussex. |
| song thrush | A range of habitats including grassland and woodland edges, using invertebrate-rich damp feeding areas |
| lapwing Vanellus vanellus | Farmland, grazing marsh, wet meadows, seeds and insects |
In Sussex, birds such as the willow tit are declining almost to extinction. bewick swans, snipe, lapwing and redshank are among those wetland birds which are declining or which are struggling to breed. The commonly seen ‘streak of blue’ of the kingfisher is also becoming less common. Due to hard winters and habitat degradation through pollution or unsympathetic management of watercourses, kingfishers are now an amber listed species.
Some wetland birds in Sussex are increasing in numbers. Common cranes have increased the frequency and number of their visits to Sussex, and the Eurasian bittern has been heard booming at a few locations. Savi’s and marsh warblers have bred in Sussex for the first time in recent years. Sussex is also a major overwintering area for pale-bellied brent geese. More detailed information on distribution and status of birds is available in the British Trust for Ornithology’s Bird Atlas.