Free-living hens perch on branches in trees and domestic hens (Gallus gallus domesticus) show signs of unrest if they cannot reach a perch, suggesting that night-time perching is a behaviour that hens are motivated to perform. This motivation was quantified in two experiments using a weighted push-door that hens had to push open in order to gain access to a perch. First, the motivation of individual birds to perch, and second, the effect of a companion bird on perching motivation, were measured. Eight adult laying hens (Lohmann Selected Leghorn) were trained to push through the door at increasing resistances, and the individual capacity of each hen was determined. Hens were then tested once per day, at lights-off in a test pen where pushing through the push-door gave access to the resource. Two consecutive series of increasing resistances were used in the experiment: 25, 50, 75 and 100 per cent of each bird's maximum capacity. In the first experiment, the resources offered were either a perch (treatment) or a ‘sham perch’ that could not be used for perching (control). Hens opened significantly heavier doors in order to gain access to a perch than to gain access to the sham perch. In the second experiment, pushing through the door gave access either to a perch with a companion hen already perching on it (treatment) or to a perch and a companion hen roosting on the floor (control). In this comparison, four of the hens did not push through the door, probably because of aggressive interactions with the companion, and no significant differences between treatments were found. We conclude that hens are motivated to use a perch for night-time roosting and that they should be housed in systems with perches.

EU-Directive 1999/74/EC stipulates that furnished cages and non-cage systems for laying hens should be provided with perches. This Directive allows for a wide variety in perch design features possibly affecting perch use and hen health. Perch material and shape mainly affect slipperiness and grip quality and, in this regard, plastic, metal and circular perches are inferior. The incidence of bumble-foot and keel bone deformities can be influenced by perch shape. Perch shapes which reduce localised pressure on the foot pad and the keel-bone are recommended. Several aspects of the arrangement of the perches in the cage or non-cage system are also important. A consistent preference for high perches is seen, provided there is a minimal distance of 19–24 cm between perch and roof. Accessibility of high perches should be ensured, for example by incorporating lower level perches from which hens can reach the higher levels. Such multi-height perch designs also allow behavioural differentiation according to perch height (with most passive behaviour on the higher perches). In non-cage systems, good accessibility can be achieved by minimising the angles between perches at different heights to smaller than 45° and by limiting the distance between horizontal perches to 1 m. The legislated minimum perch length provided per hen (15 cm) adequately allows for synchronised roosting behaviour on straight perches. However, in crosswise perch designs, hens require more perch length per hen as the area close to the cross cannot be used optimally.

The social structure of three sympatric bat species occupying bat boxes in woodland in southern England was studied: Pipistrellus pipistrellus (pipistrelle), Plecotus auritus (brown long-eared bat) and Myotis nattereri (Natterer's bat). Before parturition, P. pipistrellus populations were heavily skewed towards solitary males. After parturition, the sex ratio was closer to unity. Recaptures of marked bats suggested that after parturition a resident male population of P. pipistrellus is invaded by a transient female population. The sex ratios of populations of P. auritus and M. nattereri were very close to unity, both pre- and post-parturition. The numbers of recaptures of individual bats were similar for both sexes in P. auritus and slightly higher for females in M. nattereri. In the mating season (August-October), solitary male P. pipistrellus were found with small groups (1-9) of females. In contrast, in both P. auritus and M. nattereri, mixed sex groups were found pre- and post-parturition, and roosting groups in the mating season contained up to 20 females and up to 10 males. The stability of female groups in P. auritus appeared to be higher than M. nattereri and P. pipistrellus as known females were found together more frequently. These patterns are discussed with reference to the possible differences in foraging and social behaviour.