Productivity • Invertebrates • Birds
Fish • Amphibians • Mammals

Birds

Saltmarshes are an extremely important habitat for a number of bird species which use them for a variety of purposes, including roosting, feeding, moulting and breeding. Throughout the seasons bird numbers fluctuate markedly, with greater densities occurring during the winter months. Successful breeding by a variety of birds occurs on the upper levels of open saltmarshes following the high spring tides in April and May. Of the seven or so species of birds which breed on saltmarshes, only the Redshank (Tringa totanus) occurs in significant numbers. Approximately 50% of the UK ’s breeding population of redshank, which represents about 15% of the total breeding population of NW Europe, is supported by saltmarsh habitat (Norris, 2000). Of this around 1.5% occurs on the Wash, making this site internationally important for breeding redshank (Norris, 2000). In addition, transitional reedbeds and other marginal vegetation can be particularly valuable for rare species such as bearded tit and Savi's warbler. The structural diversity of the marsh is of crucial importance to some species, such as redshank, and high population numbers may be present in the best habitats.

Estuaries are particularly important for wintering wildfowl and waders, as they frequently support nationally and internationally important numbers of several species, most notably pink-footed goose (Anser brachyrhyncus), barnacle goose (Branta leucopsis), brent goose (Branta bernicla) and wigeon (Anas penelope). These birds feed on a variety of intertidal vegetation, ranging from common saltmarsh grass (Puccinellia maritima) to eel grass (Zostera spp.), as well as agricultural grasslands and arable crops. Pioneer and low marsh vegetation, such as Salicornia and Aster tripolium, also provide an important feeding habitat for twite (Carduelis flavirostris), which consumes the numerous seeds produced by these plants.

Of the wading birds, only redshank and snipe use saltmarsh in preference to the exposed tidal flat, probably because they like to be sheltered from view by the cover of vegetation. For these species, the saltmarsh represents the primary feeding location throughout most of the tidal cycle.

Other species, mainly grazing ducks and geese, use the saltmarsh itself as a source of food. The geese seek out open areas with close cropped or low vegetation and, even here, there are distinct preferences; while the brent goose preferentially feeds on eel grass (Zostera spp.) in the low marsh, the stronger grey-lag goose feeds on the tougher grasses of the marsh itself. Of the ducks, the wigeon feeds on both low and high marsh, normally at the water’s edge. For most of these species, the more palatable grasses favoured under high stocking densities of cattle and sheep are important to the continued use of the saltmarsh as a food resource.

Saltmarshes are also often particularly important for the smaller passerines, such as skylark, twite, reed bunting, rock pipit and Lapland bunting; some of which are winter visitors.