Access to perches for laying hens is a critical welfare provision that improves bone strength, reduces fractures, and allows expression of the strong roosting motivation that hens are highly motivated to perform.
The welfare case for perch access in laying hens is supported by both behavioral and physical health evidence. Hens are strongly motivated to perch, working hard in operant conditioning experiments to access perching opportunities even when other resources are freely available. The behavioral deprivation of cage systems is paralleled by the physical harm of severe osteoporosis — laying hens in battery cages mobilize calcium from bones for eggshell production without the weight-bearing exercise that would maintain bone density, leading to fractures that cause pain during the normal activities of life and at the time of capture and slaughter.