RESUMO
BACKGROUND: Understanding which intrinsic and extrinsic factors dictate decision-making processes such as leaving the natal area or not (migratory vs resident strategy), departure time, and non-breeding destination are key-issues in movement ecology. This is particularly relevant for a partially migratory meta-population in which only some individuals migrate. METHODS: We investigated these decision making-processes for 40 juvenile greater flamingos Phoenicopterus roseus fledged in three Mediterranean colonies and equipped with GPS-GSM devices. RESULTS: Contrary to the body size and the dominance hypotheses, juveniles in better body condition were more likely to migrate than those in worse conditions, which opted for a residence strategy. Flamingo probability of departure was not associated with an increase in local wind intensity, but rather with the presence of tailwinds with departure limited to night-time mostly when the wind direction aligned with the migratory destination. Moreover, a positive interaction between tailwind speed and migration distance suggested that juveniles opted for stronger winds when initiating long-distance journeys. In contrast to previous studies, the prevailing seasonal winds were only partially aligned with the migratory destination, suggesting that other factors (e.g., adults experience in mix-aged flocks, availability of suitable foraging areas en route, density-dependence processes) may be responsible for the distribution observed at the end of the first migratory movement. We found potential evidence of sex-biased timing of migration with females departing on average 10 days later and flying ca. 10 km/h faster than males. Female flight speed, but not male one, was positively influenced by tailwinds, a pattern most likely explained by sexual differences in mechanical power requirements for flight (males being ca. 20% larger than females). Furthermore, juveniles considerably reduced their flight speeds after 400 km from departure, highlighting a physiological threshold, potentially linked to mortality risks when performing long-distance non-stop movements. CONCLUSION: These results suggest that not only intrinsic factors such as individual conditions and sex, but also extrinsic factors like weather, play critical roles in triggering migratory behaviour in a partially migratory metapopulation. Furthermore, social factors, including conspecific experience, should be taken into consideration when evaluating the adaptive processes underlying migration phenology, flight performance, and final destination selection.
RESUMO
The presence of wildlife in areas with a high concentration of farming activities can create a conflict between conservation objectives and productive purposes. Near Brindisi (Apulia, S-E Italy), a substantial amount of cash compensation claims for damages reported by local farmers and attributed to starlings (Sturnus vulgaris) has been registered. The aim of this study was to quantify the starling population wintering in the Apulia region, in order to assess the potential damage to crop production caused by this species. Our analysis was conducted over three years and included three main activities: a study of starling abundance and movements, the identification of areas and crops affected by damages, and a determination of the damage to the agricultural system in terms of quantity and concentration (heatmap). The study showed a loss of expected production that was coherent with the eating capacity of starlings wintering in the region. This means a loss, in terms of gross profitable production, of around 550,000 euros concentrated in a few narrow areas close to the roosts. Results on species behavior, damage quantification, and mapping are useful elements aimed to activate trade-off measures to preserve production and protection objectives, and to allow policymakers to address enforcement interventions and to establish parameters for financial compensation.
