No abstract

Summary Although the population of Griffon Vulture Gyps fulvus is significantly increasing in Europe, in Italy the species is still on the Red List as ‘Critically Endangered’, with the last natural population persisting on the island of Sardinia. Several episodes of poisoning hampered the success of conservation actions implemented in the years 1987–1995. In 2005 there were estimated to be only 31–32 territorial pairs, with the population occupying the territories of Alghero and Bosa. We used a long-term dataset of reproductive records from the Sardinian Griffon Vulture populations to run a population viability analysis (PVA) to evaluate the extinction risk using the Vortex simulation software. The model estimated the probability of extinction over the next five generations (estimated generation time: 11 years, simulation time used: 55 years) as 96.4% for the Alghero population, and near-zero for the Bosa population. We used sensitivity analyses to understand how uncertainty about parameter values affect model outcomes. Population projections were evaluated under different management scenarios tackling the main threats (poisoning and human disturbance) and implementing conservation actions (supplementary feeding and restocking). Our results showed that population size is a critical factor in affecting the projections of population dynamics of Griffon Vultures. Sensitivity analyses highlighted the importance of poisoning events to population persistence and showed that juvenile and adult mortality rates had a secondary impact on population viability. The only conservation measure effective in significantly increasing stochastic growth rates in the Alghero population, whose initial population was set at five individuals, was the complete removal of poisoning events. When targeting the Bosa population (initial population size 94 individuals), supplementary feeding, mitigation of the risk of poisoning episodes, restocking, and mitigation of human disturbance in the reproductive sites significantly increased stochastic growth rate. A cost-effectiveness analysis should be performed to prioritise interventions.

Wind energy is developing on Mediterranean islands, where endangered populations of Griffon Vulture (Gyps fulvus) occur. As griffons are subjected to collisions with wind turbines while foraging, it is necessary to understand which factors affect their movements, to minimize the potential impact of wind farms.We assessed habitat use by 37 griffons (n. GPS locations = 130,218) and its overlap with wind farms in Sardinia (Italy), an island where griffon vulture population is increasing thanks to concrete conservation actions and wind energy is significantly expanding.Griffons in Sardinia cover smaller areas (95% isopleth = 956.3 ± 677.7 km2, 50% isopleth = 73.8 ± 48.2 km2) than in mainland Europe, restricting most of their movements within 5-10 km from colonies and roosts.Concentrated movements aligned with the fact that around roosts and colonies, approx. 20 tons of carrion (21% of estimated available carrion) are provided each year in supplementary feeding stations, while griffons still have enough cliffs to breed. Therefore, our results are highly suggestive that resource availability can constrain griffon movements on Mediterranean islands.Overall, 6 wind farms out of 29 were built in areas that were covered by moving griffons. Two of them were positioned right outside the areas the most used as foraging grounds, around roosts and supplementary feeding stations.As griffon movements concentrate around nesting/roosting sites and feeding stations, wind farms should not be built in a buffer zone around these highly utilized areas, and mitigation measures, including the removal of livestock carrion, should be adopted for those that are built at greater distances. There is also an urgent need for updated data about wind energy development. The creation of supplementary feeding stations could be used to shape the enlargement of the foraging grounds of an increasing Griffon Vulture population on Mediterranean islands and to mitigate wind farms impacts.

In the 19th century, Red kite (Milvus milvus) was very common and widespread in Sardinia, but in the mid-900 an important decline occurred. Since the 1970s the species has been studied more continuously, but in recent years the published data seem contradictory. In 2018-2020, authors carried out specific research to collect data on the population of the Red kite in Sardinia exploring both the historical range of the species and areas where the species was reported in the past. In 2018-2020, we estimated 10-13 breeding pairs in an area of about 3,440 km2 located in the north west of Sardinia. As regard wintering, we estimated 30-40 birds in winters 2018-2019 and 2019-2020, whereas 90-110 birds were counted in winter 2020-2021.

No abstract