I share your high regard for animal welfare, which I am pleased is protected by comprehensive and robust legislation. The Animal Welfare Act 2006 already makes it an offence to cause any unnecessary suffering to any animal, including gamebirds.
This is backed up by the statutory Code of Practice for the Welfare of Gamebirds Reared for Sporting Purposes. The code recommends that when birds are housed or penned, the accommodation should be well constructed and managed and of sufficient size to ensure good health and welfare. Specifically, the code recommends that barren raised cages for breeding pheasants and small barren cages for breeding partridges should not be used and that any system should be appropriately enriched. Keepers are required by law to be familiar with this code, which encourages the adoption of high standards of husbandry. Failure to observe the provisions of this code may be used in support of a prosecution.
These rules are enforced by the Animal and Plant Health Agency, as well as by local authorities, who can both carry out routine welfare inspections and investigate complaints. Prosecutions can be brought where necessary.
I am pleased that the Government has taken action to ban cages or close confinement systems where there is clear scientific evidence that they are detrimental to animal health and welfare. For example, the use of battery cages for laying hens has been banned since 2012.