The H5N1 virus caused thousands of deaths in seabirds. Dozens of different species of wild birds were hit, including golden eagles, buzzards, herring gulls and gannets.
Mammals were also infected, including otters, foxes, seals and dolphins.
Meanwhile, there were hundreds of outbreaks at poultry farms, with four million farm birds culled.
Free-range poultry was ordered to be brought inside in England, Wales and Northern Ireland, to avoid the birds coming into contact with wild birds.
In Scotland the housing order was never implemented after the country's chief vet said the evidence did not justify such a move.