The reserve covers 550 hectares and includes a variety of habitats extending inland from mudflats and salt marsh through farmland and pools to oak woodland and hillside scrub.
The woodlands hold redstart, wood warbler and pied flycatcher while red kites frequently pass overhead.
Wintering birds include many ducks such as shelduck, wigeon and teal and waders such as oystercatcher and curlew.
The reserve has also attracted nationally rare bird species, such as a gull-billed tern in July 2015.
According to the BBC, the move from Pensthorpe Nature Reserve in Norfolk took a year of planning.