31 October 2016 Last updated at 08:53 GMT
Pheasants and partridges, used to breed chicks for shooting estates across the UK, are being confined in barren, wire mesh cages, under conditions that are worse than those allowed for chickens.
Inside Out London discovered shocking conditions at three breeding sites.
Watch the full report on BBC Inside Out London on Monday 31 October at 19:30 on BBC One.
Tens of thousands of game birds are being held in cages which can lead to injuries and premature death, a BBC investigation has uncovered.