Aviary systems represent the primary cage-free housing technology for laying hens, but their welfare outcomes depend critically on design, management, and stocking density rather than system type alone.
Aviary system welfare is highly contingent on management quality in a way that simpler caged systems are not. A well-managed aviary with trained birds, appropriate stocking density, excellent litter quality, and attentive stockpeople delivers substantially better welfare than any battery cage system. A poorly managed aviary with high mortality, endemic respiratory disease, and pervasive keel fractures may deliver worse outcomes than some enriched cage systems for specific welfare measures. The lesson is that aviary systems are a necessary but insufficient condition for high laying hen welfare — they must be paired with the management expertise and investment to realize their potential.