Definitive requirements are set out in the published declarations for each disease control zone currently in force. For further information see the ‘Cases and disease control zones’ section on GOV.​UK: https://www.gov.uk/guidance/avian-influenza-bird-flu-cases-and-disease-control-zones-in-england#cases-and-disease-control-zones

You can also check if specific areas are in a zone by using the interactive map available on GOV.​UK: https://defra.maps.arcgis.com/apps/webappviewer/index.html?id=8cb1883eda5547c6b91b5d5e6aeba90d