The prolonged cold is surely enough for at least voluntary bans on wildfowling. Hunters have been seen in Wales still going out even though wildfowl are struggling to find ice-free conditions to roost and feed.
Those ornithologists regularly ringing should also consider whether their normal operations are viable for the birds. Keeping birds away from food in the current icy conditions for even 15 minutes might be enough to affect their wellbeing.
For more details on how both these operations should be conducted try www.jncc.gov.uk/page-2894 and also http://www.wildfowling.com/