Duncan, E. T., Appleby, M. C., Hughes, B. O. 1992. Effects of perches in laying cages on welfare and production of hens. British Poultry Science 33, 25-35.

Caged hens spent 25 to 50% of the light period and around 85% of the dark period roosting on perches. Perches with a rectangular cross-section caused less damage to the feet of birds than those with a circular cross-section.