What influences feather care and unipedal resting in flamingos? Adding evidence to clarify behavioural anecdotes

Flamingos (Phoenicopteriformes) are relatively well studied species of bird, both in the wild and in captive environments. Arguably, the two most famous anecdotes surrounding flamingo behaviour concerns their time spent on one leg (what is this related to?) and time spent preening (is it more than other species of waterbird?). We conducted an observational study at WWT Slimbridge Wetland Centre on five species of flamingos to test whether empirical evidence supported these anecdotes. We coupled this observational study with a global meta-analysis of published data on waterbird preening behaviour to allow a comparison of flamingos with other large waterbird taxa (Anseriformes, Ciconiiformes, Gruiformes, and Pelecaniformes). Analysis using zero-inflated generalised linear models indicated that flamingo unipedal behaviour was more common inside housing and on water. Preening effort varied markedly between flamingo species, but we detected no influence of any of the weather variables that were tested. Furthermore, our meta-analysis of waterbird behaviour indicated an interaction between latitude and season, whereby birds spent more time preening at higher latitudes during the non-breeding season, but the opposite trend was detected during the breeding season. Contrary to the popular perception, we found no evidence that flamingos spend more time preening than other waterbirds; indeed, our analysis indicated that, among the five waterbird orders assessed, Pelecaniformes preened the most. However, waterbird preening effort was higher for captive populations (across all species) relative to their free-living counterparts. Our study provides new insight into long-held perceptions of the behaviour of flamingos and other waterbirds.