The site is notified for its large areas of intertidal sand and mudflats, which support internationally important populations of Turnstone (Arenaria interpres), Redshank (Tringa totanus) and nationally important populations of Cormorant (Phalacrocorax carbo).
The Mersey Narrows is located at the mouth of the Mersey Estuary and comprises Seaforth on the north bank and Egremont Foreshore on the south.
The two areas are separated by approximately 2 km, but considered to be an integral site on the basis of the constant interchange of bird populations. Whilst Egremont Foreshore is particularly important as a feeding site at low tide, Seaforth is particularly important as a high tide roost site, particularly during high spring tides when rocky shores and man-made structures closer to the feeding areas are submerged and not available as roosting sites.
Seaforth is located to the north of the Royal Seaforth Dock on land claimed from the sea during the 1960's. The River Mersey lies to the west. The site now consists of a complex of open water, saltmarsh and grasslands. Specifically it comprises two lagoons, a shallow water lagoon which functions as a settlement lagoon for water pumped from the River Mersey into the Seaforth Docks and a freshwater lagoon separated from the saltwater lagoon by a wide bund.
The freshwater lagoon is dominated by the aquatic species, Water-milfoil (Myriophyllum spicatum) whilst the fringing vegetation is characterised by Sea Club-rush (Bolboschoenus maritimus), Red Goosefoot (Chenopodium rubrum) and Spear-leaved Orache (Atriplex prostrata).
A strip of saltmarsh occurs along the western edge of the saltwater lagoon. Although inundation is constrained due to pumping operations, a number of species are present including Glasswort, also known as Marsh Samphire.
English Nature citation details:
Date Notified: 9th August 2000
File Ref: SJ 39/5
Site Name: Mersey Narrows
Status: Site of Special Scientific Interest (SSSI) notified under Section 28 of the Wildlife and Countryside Act 1981(as amended).
Local Planning Authority: Wirral Metropolitan Borough Council & Sefton Metropolitan Borough Council
National Grid Reference: SJ 315 949
Area: 129.02ha. 318.68ac.
Ordnance Survey Sheet 1:50,000: 108
Date Notified (under 1949 Act):
Date Notified (under 1981 Act): 2000