The Common is very quiet in December so there is an opportunity to go further afield.

A visit to the RSPB site at Pulborough Brooks will allow you to see the wintering wildfowl and also stock up on birdfood and unusual nature-oriented Christmas presents.   You don't need to be a member.   There is a pleasant cafe in a wonderful wooden building - just right for a hot drink a food after the walk.

A wonderful after Christmas walk is around Pagham Habour in Sussex.  Take binoculars since the the harbour is large and the birds can be some way off.    Park at Church Norton; wear wellies; take your own thermos and picnic because there is nothing on site.