Social roles and resource competition mediate intraspecific interactions of Chilean Flamingo (Phoenicopterus chilensis) in southern Brazil

Abstract

In social birds such as flamingos, intraspecific interactions are frequent and play a key role in flock cohesion, communication, and the establishment of social networks. These behaviors can reduce competition stress and enhance protection, but their nature and underlying motivations vary. Understanding the patterns and drivers of these interactions can provide valuable ecological insights and inform management, husbandry, and conservation practices. We observed agonistic intra-flock interactions in a wild population of Chilean Flamingo (Phoenicopterus chilensis) at Lagoa do Peixe National Park, southern Brazil. Data were collected on the interactions, flock composition, and environmental conditions. Based on the individuals involved, their characteristics, and the nature of behavioral displays, we classified interactions into three types: unilateral disputes, bilateral disputes, and brief altercations. Using Generalized Linear Mixed Models, we analyzed the influence of flock and environmental variables on two main factors: the probability of physical aggression and the mean duration time of interactions. Our findings indicate that unilateral and bilateral disputes were primarily influenced by flock-related variables, especially during periods with more males and denser aggregations, suggesting a social-driven origin. In contrast, brief altercations were affected by both social and environmental factors, becoming longer in resource-scarce conditions, which indicates competition-driven behavior. These results highlight a dual mechanism shaping intra-flock aggression in Chilean Flamingos: social roles and resource competition. This complexity reveals a fundamental trade-off in group living, between the safety of sociality and the costs of increased conflict, offering important perspectives for the ecological understanding of this and other social species.