Welney Wetland Trust is about 20 minutes from Littleport and can be a great day out any time of the year.
During the winter (late October to early March), they have feeds for the swans that migrate to the local area. Check the times to confirm but when I went you could go at midday and 3.30 pm everyday and 6.30 pm floodlight feeds Thursday to Saturdays.
It was good because they gave you the history of the site and trust, how people used it, and told you what birds you are looking at. Quite handy for a person like me who knows nothing.
They have so much more to offer than just these feeds.
Outside of these things, they have many walks that you can do, bird feeding station, Fenland worlds exhibition, Pond Room, Main observatory, Dragonfly ponds and the Lyle hide.
Great day out with the children in nature.
They also have a cafe to fill your stomach after being one with nature.
You can see some of my photos here.