85. Birds may display fear in response to different types of stimuli in all systems. For birds exposed to a relatively unvarying indoor environment, any sudden visual or auditory stimulus may be frightening. The almost universal practice of knocking on the door or speaking before entering a hen house indicates the likelihood of panic reaction that the unexpected appearance of a person might induce in a flock. Particularly in colony houses, such panic reactions can lead to injury and, in extreme cases, suffocation if large numbers of hens rush to the far end of a building or pen in alarm. In the more varied outdoor environment, hens tend to display different types of fear reaction. Wild birds flying overhead may induce a specific predator avoidance reaction, involving high levels of fear. Low level balloon flights or aircraft may cause similar reactions. Regular observation and good management are particularly important when birds are allowed to range and the hens should be returned to the house at dusk and closed in the house for the night.
86. Distress, pain and suffering will inevitably result from outbreaks of injurious feather pecking or cannibalism.
87. Protection from predators is essential. It is well established that predators, and also fear of predation, are important elements in the life of a hen particularly in the more extensive systems. Predators cause welfare problems both directly, causing injury and death and indirectly, by inducing fear.
88. Where hens are kept extensively and may be free to range it is important to provide some overhead shelter and to ensure that they are protected from predators by day and confined in the building during the hours of darkness.