COUNTRYSIDE COUNCIL FOR WALES
SITE OF SPECIAL SCIENTIFIC INTEREST: CITATION
ANGLESEY MALLTRAETH MARSH / CORS DDYGA
National Grid reference: SH440710
Site Area: 1,366.5 ha
This site has been selected for its biological interest. It is especially important for its breeding bird community of lowland damp grassland, as a threatened habitat of wet meadows, and for the botanical interest of its ditches and watercourses.
Malltraeth Marsh has developed on marine alluvium within the low-lying valley of the Afon Cefni. In 1810 the erection of an embankment to exclude the sea, and measures to reduce flooding through a network of ditches and the canalisation of the River Cefni, enabled its reclamation for agriculture.
The botanical interest of the marsh lies in the freshwater and brackish ditches, relict meanders of the old River Cefni, ponds and lakes. Emergent species such as reed canary-grass Phalaris arundinacea, water-plantain Alisma plantago-aquatica and branched bur-reed Sparganium erectum are frequent dominants. Amongst the species of importance in Wales reed sweet-grass Glyceria maxima horned pondweed Zanichellia palustris, flowering rush Butomus umbellatus, water violet Hottonia palustris, mare's tail Hippuris vulgaris and marsh stitchwort Stellaria palustris. Two nationally scarce species, pillwort Pilularia globulifera and autumnal starwort Callitriche hermaphoditica, occur.
The breeding birds community of lowland damp grasslands on the marsh includes mute swan, shelduck, shoveler, lapwing, curlew, redshank, snipe grasshopper warbler, sedge warbler and reed bunting. Other breeding species include buzzard, kestrel, reed warbler and tufted duck. There is a small heronry on the site. Bittern has been heard booming in recent years and marsh harrier, black tailed godwit and ruff, all potential breeders, have been recorded in the spring and early summer. The marsh provides feeding grounds for migrating and wintering waders and wildfowl including the important pintail population in the Cefni estuary.
Amongst the eleven sepecies of dragonfly recorded, three are nationally scarce: the hairy dragonfly Brachytron pratense, the variable damselfly Coenagrion pulchellum and the scarce blue-tailed damselfly Ischnura pumilio. Some notable water beetles occur such as Loccobuis sinuatus and Rhantus grapii.