The Heswall course provides an excellent view of the Dee Estuary and the Welsh Clwydian hills beyond. Visibility of the river itself has rapidly decreased over the centuries as the river has silted up. Land reclamation and canalisation of the river in the eighteenth century resulted in the main river channel permanently following the Western, Welsh shore with extensive sand and mudflats developing on the eastern, Wirral side. Colonisation of these, by both naturally occurring vegetation and Spartina anglica (common cord grass), which was planted since 1929 to stabilise reclaimed land, has led to large areas of saltmarsh which are still expanding today.
During the high spring tides, especially if these are accompanied by low atmospheric pressure and north westerly winds, the marshes are submerged under salt water for a short period.Â During the remainder of the year, the water in many areas near the shore becomes brackish due to local springs and streams from the natural aquifer under this part of the Wirral and, to a lesser extent, fresh water run-off from adjacent land. This has resulted in changes in the vegetation, for example the development of reed beds in boggy areas.
A large colony of grey seals has built up in the estuary and nearby parts of Liverpool Bay. At low tide these haul out onto the sandflats at West Hoyle Bank. Common seals, dolphin and porpoise have also been spotted in the estuary.
The extensive inter-tidal sand and mudflats are of great importance because they provide major feeding areas for birdlife.
The estuary is one of the top 10 wetland sites in Europe because of the numbers of wildfowl resident and overwintering. At least 12 species are present in such numbers, that the Dee Estuary is recognised as being a nationally and internationally important location. As a result, it has been designated a site of special scientific interest (SSSI), a special protection area (SPA) and a sensitive marine area (SMA). Up to 110,000 waders and 20,000 wildfowl populate the estuary, especially in winter. These include shell duck (10,000) and pintail (5,000). Other species present in significant numbers include redshank, knot and dunlin.
This amount of potential prey, together with animals occupying the saltmarsh, attracts a range of avian predators such as short-eared owls, marsh and hen harriers, peregrine and merlin.
In recent times, other species have expanded their range north to the Dee Estuary from mainland Europe. There is now a large resident breeding colony of Little Egrets at RSPB Burton Mere Wetlands and this has been joined in summer by a breeding flock of Avocet. Spoonbills and Great White Egrets are also regularly seen although not breeding (yet).
Every winter over 80,000 birds as well as 30,000 duck and wildfowl, are drawn to the estuary for the abundance of food such as worms, snails, other crustaceans and invertebrates.