VISUAL RECOGNITION OF KEY NEST-SITE STIMULI BY LAYING HENS IN CAGES

Laying hens (64 medium-hybrid ISA Browns), which had been kept to 50 weeks old either in pens or in battery cages, were placed in individual cages which had a tray covered with a thin layer of wood-shavings litter under part of the cage floor; these trays could be seen but not touched by the birds. A majority of previously penned birds, with experience of littered nest sites, responded to the trays by sitting and laying their eggs on the wire floor over them: in the first experiment six out of ten birds showed tray preferences, while in the second experiment it was 16 out of 20. In contrast, the previously caged birds were either indifferent to the trays or avoided them. It was concluded that merely a visual stimulus which had some of the features of a nest site was sufficient to trigger a nest-orientation response in hens with experience of nests, whereas in birds which had only experienced cages the positive response was entirely absent, showing they did not visually recognise a flat, littered surface as a preferred nest site.