Flock size during rearing affects pullet behavioural synchrony and spatial clustering

Abstract

Highlights• Behavioural synchrony and clustering in space decreased with increasing bird group size.• Preening was the most synchronised over time and feeding the most clustered in space.• Simultaneous access to resources for all is more important in small than large groups. AbstractAnimals are often synchronised in their behaviour, with costs and benefits varying according to group size and the behaviour being performed. Making decisions about optimal allocation and distribution of resources to animals in our care therefore poses theoretical and practical challenges. We investigated group size effects on behavioural synchrony and spatial clustering during daytime in pullets of a commercial laying hen strain reared until 18 weeks of age in groups of 15, 30, 60 and 120 (four replicates of each group size). Feeder, drinker, perch and litter space (i.e. floor space allowance) per bird, were constant across group sizes and all resources were continuously available. Even though the absolute numbers of birds performing the same behaviour at the same time or being located together at the same resource patch increased with increasing group size, the relative degree of synchrony of feeding, drinking, perching and preening across the whole flock decreased exponentially with increasing group size (P < 0.001 for all behaviours) as did the relative degree of clustering at the same resource patch (P < 0.001 for the same four behaviours). Preening was the most synchronous behaviour (more than twice that of the least synchronised behaviour, perching), and feeding the most clustered in space (three times more clustered than the other behaviours). These results imply that it is more important to provide sufficient resource space for all birds to perform daytime activities simultaneously when kept in the smaller group sizes typical of cages, than in the larger flocks typical of birds kept in floor pens and aviaries.

Black-headed gulls synchronise their activity with their nearest neighbours

“…Synchrony within groups can emerge through social facilitation 28 – 30 , where an individual is more likely to conduct a behaviour when in the presence of another individual that is already engaged in conducting the behaviour. Alternatively, synchrony can result from some external local influence or zeitgeber 31 , 32 causing similar responses to occur in multiple individuals at the same time. Studies that have suggested that synchronisation is induced by local stimuli usually consider behaviours that require individuals to be aggregated at a local resource, such as foraging behaviour seen at a feeder ( e .…”

“…g . 32 – 34 ). The loafing behaviour we recorded here is less likely to be either clustered or influenced by local stimuli than feeding behaviours, but could conceivably be driven by local habitat differences in predation risk that affect vigilance behaviour, such as exposure and proximity to cover 35 – 39 , as well as position within the group and proximity to other individuals 4 , 6 , 40 – 43 .…”

Dust bathing in laying hens: strain, proximity to, and number of conspecifics matter

“…Finally, the total number of birds DB (including the focal hen) was counted within each image, and the total number of birds present on the open litter area was counted. Synchrony can be defined as multiple animals in a group performing a behavior simultaneously ( Keeling et al., 2017 ). For this study, we looked at hens DB at the same time on the open litter.…”

Broiler Chickens On-Farm Welfare Assessment: Estimating the Robustness of the Transect Sampling Method

“…To test the differences in distribution between the expected and the observed number of marked birds, we calculated the distribution index according to the formula by Keeling et al (25): false(N observed marked birds in transect–N expected marked birds in transectfalse)2N expected marked birds in transect The expected number of marked birds/transect was estimated according to the specific transect dimensions. The distribution index tends to be zero when the observed and expected number of marked birds are similar, indicating a random bird distribution.…”