Flocking Hierarchy in European Starlings

Structured hierarchies in animal groups have long been observed to play a crucial role in food acquisition, territories, movement, and migration. In particular, birds display strong tendencies of social dominance in regard to flock behavior, mate choosiness, and territory exclusivity. In this study we examined flight patterns in European Starlings, Sturnus vulgaris, to determine whether there was an observable hierarchy, or linear order, when flying in an animal flight wind tunnel and whether or not any observed hierarchy was related to other physiological factors. Experiments were conducted using an animal wind flight tunnel to fly single, pairwise and triplet flights of starlings. Video recordings of these flights were then analyzed to determine whether starlings indeed follow a linear order when flying and later compared to physiological factors measured from the bird. Analysis of the resulting dataset built of paired, or occasionally three-bird groups revealed a linear dominance hierarchy for flock role. Furthermore, leadership was significantly correlated with other physiological variables; birds that were larger by mass and had lower metabolic cost of flight (i.e. greater flight efficiency) were more likely to be leaders. Meaning, the better the flier the more likely it was to be flying in front, allowing the other birds to drift in its wake, or alternatively being more able to outcompete other birds for a preferred flight position. Our results will add to the broader study of flight behavior in starlings, and possibly other birds, enabling a deeper understanding of sociological behavior of birds and what role they play in flight, migration, and ultimately, survival.