What influences aggression and foraging activity in social birds? Measuring individual, group and environmental characteristics

Abstract

For specialised feeders, accessing food resources may impact on the performance of appetitive foraging and social behaviours at individual and population levels. Flamingos are excellent examples of social species with complex, species‐specific feeding strategies. As attainment of coloured plumage depends upon intake of dietary carotenoids, and as study of free‐ranging flamingos shows that foraging is disrupted by aggression from other birds, we investigated the effect of four feeding styles on foraging and aggression in captive lesser flamingos. We evaluated individual and group differences in foraging and aggression when birds consumed bespoke “flamingo pellet” from a bowl, an indoor feeding pool and an outdoor feeding section of their pool. Natural foraging (when birds were feeding irrespective of the presence of pellet) was recorded for comparison with artificial feeding styles. One‐minute long video footage of the birds' activities in these different locations, recorded between 2013 and 2016, was used to evaluate behaviour. Total number of seconds engaged in feeding and in aggression was recorded by continuous sampling. The colour of individual birds was scored from 1 (mainly white) to 4 (mainly pink). For natural filter feeding in the outdoor pool, maximum foraging was twice as much as bowl feeding, whilst aggression was less than half as much as other feeding methods. Overall, a more restricted feeding style significantly predicted aggression, along with increasing group size. Plumage colour significantly influenced aggression (brightest flamingos were more aggressive) and showed a non‐significant trend with foraging (brighter birds fed less than paler birds). No sex effect on feeding or aggression was found. This study enhances our understanding of husbandry and species' biology impacts on captive behaviour and provides data‐based evidence to improve food presentation. For flamingos, implementation of spacious outdoor feeding areas can encourage natural foraging patterns by reducing excess aggression and enhances welfare by improving flock social stability.