The Leigh mudflats are known locally as Leigh Green. This is due to the covering of eelgrass (zostera marina) which, in the Autumn, gives the mud a green sheen. The eelgrass helps to attract wildfowl to the area.

The Thames Estuary is strongly tidal, with an average rise and fall at Southend pier of around 19 feet at Spring tides. Leigh, once a small deep water port, is now so silted up that the tide goes out over about a mile of mudflats and on these mudflats grow the eel-grass which the wildfowl feed on at low water

The main quarry species on Leigh Green are Widgeon, Mallard and Teal. Pintail, Shoveller and Pochard are occasional visitors.

The Green is visited every year by large numbers of Brent Geese. There can be so many that the flocks look like dark clouds crossing the evening sky. They normally arrive in October and the main flocks leave during November but some stay to feed on the local farm lands.