Bird preferences

In WP4 the behaviour and preferences of laying hens using the proposed enrichment features for furnished (enriched) cages, namely perches, nesting and dustbathing areas and increased space are reviewed. These facilities are also relevant for other non-cage systems.

A few studies have shown that hens are prepared to work to gain access to perches at night, but there has been insufficient research work to know the extent to which perching is a behavioural priority. When perches are provided, hens make use of them, with up to 100% of birds perching at night. In the absence of perches, they choose to roost on the highest fixtures and fittings available and it is possible that these could satisfy their behavioural needs. Particularly in spatially restricted environments hens may use perches to obtain more space, and social factors may influence the use of perches. The value of perches for the physical and physiological welfare of laying hens is discussed in other WP sections.

Considerable research on nesting and pre-laying behaviour indicates that hens not only have a preference for a discrete, enclosed nest site but also that they value it sufficiently to work hard to gain access to one in the period (approximately 40 minutes) before egg-laying. They appear to have an instinctive need to perform pre-laying (nest-building) behaviour for about 20 minutes before laying. Thus in practical terms, enclosed nest-boxes should be provided with access available to hens from about an hour before the first bird is expected to start laying. The number of nesting areas provided should be sufficient to enable all hens to spend an average of about 30 minutes in a nest box. There is no need for the nest boxes to be available after all birds have finished egg laying (i.e. during the afternoon and night).

Despite considerable research effort, scientists have not definitively discovered the extent to which hens value dustbathing. This is in part due to effects of rearing experience and in part to the fact that litter may be used for foraging and egg laying as well as for dustbathing. Some research has indicated that dustbathing in litter is not a behavioural priority but there is strong evidence that it is a behavioural need. So-called ‘sham’ dustbathing may be a satisfactory alternative particularly to birds that have not previously experienced dustbathing in litter, but further research is needed to be certain of this.

Space and social preferences
Experiments carried out at given stocking density, group size or available space do not usually apply to other levels of these variables because of their inevitable link. Bird preferences in one context may change in a different social and environmental context. Evidence suggests that laying hens need a reasonable ‘personal space’ and that priority for space may vary during the day as activity and possibly social interactions alter. The smaller the total space available to a group of birds, the larger the space per bird needs to be in order to avoid crowding and to enable behavioural needs to be met. Birds may give greater priority to space than to small group size. They may have different social strategies in small groups where they can recognise each other and in large groups (over 100) where most encounters are between strangers and this can affect levels of aggression.

Agonistic and abnormal behaviour
The presence of apparently purposeless behaviour or of high levels of aggression or redirected behaviours such as feather pecking and cannibalism are indicators that the housing system is not satisfactory for bird welfare.

4.1 Literature review on bird preferences

Deliverable 41.pdf

4.2 Report on prevalence of feather pecking in various production systems

Deliverable 42.pdf