All bird keepers are now legally required to follow strict bio-security measures to help protect their flocks.
Owners with more than 500 birds inside the Avian Influenza Prevention Zone (AIPZ) must restrict access for non-essential people.
Workers must change clothing and footwear before entering enclosures and vehicles must be disinfected regularly.
Avian influenza circulates naturally among wild birds and can be spread to poultry and other captive birds when they migrate to the UK from mainland Europe in winter.
UK health agencies say the risk to public health from the virus is very low.
The introduction of the AIPZ comes after the disease was detected in captive birds in England, Wales and Scotland, as well as among wild bird at multiple sites across the UK.
In a joint statement, the Chief Veterinary Officers for England, Scotland and Wales said: “Whether you keep just a few birds or thousands, you are now legally required to introduce higher biosecurity standards on your farm or small holding.
“It is in your interests to do so in order to protect your birds from this highly infectious disease.
“The UK health agencies have confirmed that the risk to public health is very low and UK food standards agencies advise that bird flu poses a very low food safety risk for UK consumers.”