The Mute Swan (Cygnus olor) is perhaps the most visible and best-loved resident of Widewater Lagoon. A breeding pair has been present at the lagoon for many years, raising successive broods of cygnets on the sheltered water. As the season turns, the adult birds drive their grown young away ahead of the following breeding season, and the juveniles join the wider flock of swans on the nearby River Adur before dispersing further afield. The resident pair are well known to regular visitors — the lagoon has a long tradition of its swans being given names by the local community.

The lagoon supports a surprisingly diverse range of birds throughout the year. Resident and visiting species include Little Egret, Grey Heron, Cormorant, Kingfisher, Little Grebe, Mallard, Redshank, Ringed Plover, Goldfinch and various gulls. The embankment vegetation attracts migrant butterflies and also provides cover for passage warblers and other small migrants making the Channel crossing.