Evaluating the social networks of four flocks of captive flamingos over a five-year period: Temporal, environmental, group and health influences on assortment.

Flamingos are well known for their gregarious habits and aggregations in large flocks, but evaluation of the mechanisms behind social grouping remain poorly understood. Captive birds provide a useful model for investigating aspects of social choice in highly gregarious, long-lived species. Animals invest in social relationships that convey fitness benefits and bonds can be long-lasting. For some species, field-based measurement of social networks can be difficult. Captive populations therefore provide a useful alternative for measuring social choices. Data were collected on flamingos at WWT Slimbridge Wetland Centre from 2013 to 2016 and compared to data from 2012. For three flocks, associations were analysed along with individual foot health scores to identify any relationship between health and social behaviour. Long-term partnerships were present in all flocks; preferred associates noted in 2012 were present in 2016. Matrix correlations across years were positive; arrangements of dyads, trios and quartets with higher ties strengths were visible at the beginning and end of the study. Both male-male and female-female bonds were stable over time. All flamingos were more frequently seen socialising than solitary; those in the largest flock showed the highest occurrence of social behaviour (irrespective of enclosure size differences). The number of connections realised from all available within a network was significantly influenced by season. Foot health did not predict associations in these three flamingo networks. Our results indicate that flamingo societies are complex (i.e. formed of long-standing preferential partnerships and not loose, random connections) and the impact of flock size and environment on sociality should be investigated further. These results are helpful for those working with captive flamingos to consider the number of birds housed so that an array of opportunities for choice of associate and/or breeding partner are available in zoo-housed flocks.