Intertidal mudflat and sandflats are a major components of estuarine ecosystems, with large areas supporting high densities of bivalve molluscs such as cockles (Cerastoderma edule), peppery furrow shells (Scrobicularia plana) and mud snails (Hydrobia ulvae), all of which contribute to the provision of important feeding grounds for large numbers of wading birds. The most important mudflat and sandflat areas in Wales are found in the Burry Inlet, Milford Haven, Dyfi estuary and in the Dee and Severn cross-border estuaries..