The harbour was intentionally flooded in 1910 when a storm breached the sea wall, reverting farmland back to tidal saltmarsh.
It is one of the few remaining relatively undisturbed saltmarshes in the region.
The site supports the rare Desmoulin's whorl snail, which inhabits the reedbeds.
During winter, the reserve hosts significant numbers of dark-bellied brent geese.
The Sidlesham Ferry Bridge offers a historic vantage point over the channels, dating back to when the harbour was an active shipping port.
RSPB Pagham Harbour is a 1,500-acre sheltered tidal inlet and saltmarsh located on the West Sussex coast. It serves as a critical site for breeding, wintering, and migratory birds, including little terns and avocets. The reserve encompasses diverse habitats such as reedbeds, lagoons, and woodland that support rare plant species and invertebrates. Managed by the RSPB in partnership with West Sussex County Council, the site provides a series of hides for wildlife observation. The harbour was historically land-reclaimed for farming before being breached by the sea in the early 20th century, returning the area to its current saltmarsh state. A network of public footpaths and bridleways allows access across the harbour floor and surrounding grassy banks. The site is a designated Site of Special Scientific Interest (SSSI) and a Local Nature Reserve.
The elevated boardwalk and viewing hides near the Sidlesham visitor area.
Check the tide tables before visiting, as high tide significantly changes the available walking paths and visibility of waders.
Bring binoculars or a spotting scope, as the best birding spots are often distant from the main paths.
Follow the marked paths to avoid disturbing ground-nesting birds, especially during the spring breeding season.
Attempting to walk across the mudflats during a rising tide or straying from marked paths into fenced conservation areas.
Keep dogs on a lead at all times to protect ground-nesting birds; stay on designated paths.
