Aviary systems represent a significant advance over conventional cages for laying hens by providing vertical space and behavioral opportunities, but require careful management to realize welfare benefits.
Aviary systems enable hens to express a broader behavioral repertoire than cages, including wing flapping, perching at height, and dust bathing. However, keel bone fractures from collisions represent a serious and largely unresolved welfare problem that affects the majority of aviary-housed hens. Fractures cause chronic pain that compromises welfare for much of the production cycle. Management factors including lighting levels, tier design, pop hole placement, and bird training for using the system affect whether aviaries genuinely improve welfare or simply substitute one problem set for another. Ongoing research to reduce keel bone injury is critical to delivering on the welfare promise of cage-free systems.