To Flee or Not to Flee: How Age, Reproductive Phase, and Mate Presence Affect White Stork Flight Decisions

SIMPLE SUMMARY: High levels of predation can reduce survival rates of young birds and affect overall population growth. Therefore, birds that are better adapted to avoid predators, such as through strategic nest positioning, camouflage, and loud alarm calls, have a greater chance of successfully fledging their young. This study examines how white storks adapt to potential human threats during their nesting season and shows the effects of factors such as age, reproductive stage, and presence of a mate on their nesting behavior. The results show that storks are able to adapt their defense strategies depending on the perceived value and level of threat to their current brood. In particular, during crucial breeding phases, storks tend to prolong their stay in the nest while accelerating their return, reflecting a delicate balance between immediate reproductive needs and future prospects. In addition, the influence of a mate leads to earlier departure from the nest, suggesting a possible sexual conflict and interplay between parental care priorities. These results provide a deeper understanding of the intricate decision-making mechanisms of white storks when faced with perceived threats during the breeding season. The study contributes to a more comprehensive understanding of avian behaviors in response to environmental challenges. ABSTRACT: Recognizing, assessing, and responding to threats is critical for survival in the wild. Birds, especially in their role as parents, must decide whether to flee or delay flight when threatened. This study examines how age, reproductive stage, and the presence of a mate influence flight initiation distance (FID) and nest recess duration in white storks. Analyzing the data with a generalized additive mixed model (GAMM), we found significant correlations between FID and age, reproductive stage, and presence of a mate. These results suggest that the trade-off between current and future reproduction shifts during critical breeding periods, such as incubation and nestling care. To increase breeding success, White Storks appear willing to take risks and extend their stay in the nest when offspring are most valuable and vulnerable. In the presence of a mate, individuals leave the nest earlier, suggesting possible sexual conflict over parental care. The duration of nest abandonment is consistent with FID, except for age. These results illustrate how parental age, brood value, vulnerability, and sexual dynamics influence white stork flight decisions in complex ways. Understanding these dynamics enriches our knowledge of bird behavior and adaptations to environmental challenges and highlights the complexity of parental decision making.