The Italian grey partridge (Perdix perdix italica Hartert, 1917) is a subspecies endemic to the Italian peninsula, considered extinct in the wild, and it is included in Annex I of the EU Bird Directive. The aim of our project is to reintroduce a viable population of the endemic taxon into a protected area in north-east Italy, using genetically selected founder birds belonging to the original Italian genetic lineage. From 2021 to 2023, a total of 30,078 partridges were reintroduced to Valle del Mezzano using a soft-release method, and 241 of them were equipped with VHF transmitters to evaluate survival, dispersal and spacing behaviour of the released birds. Furthermore, male spring counts using the playback method were performed to assess the number of reproductive pairs. The overall survival was 21.86%; the Cox proportional hazards model, including time-dependent effects, showed that neither sex (HR = 1.20, p = 0.28) nor body mass significantly influenced survival. The release year was included as a stratification factor, and site-level heterogeneity was negligible. These results show that survival dynamics were not explained solely by individual traits. Dispersal distance and spatial behaviour were affected by the release year, while sex had only a minor effect and body mass had no impact. Local heterogeneity contributed to variability but did not override the strong temporal pattern. The number of calling males in spring ranged from 152 to 267, with variations between years. Overall, our findings suggest that post-release performance in reintroduced individuals is influenced more by environmental factors than by inherent individual traits. In conclusion, despite high mortality rates among reintroduced birds, the first breeding nucleus of Italian partridges since their extinction in the wild has been observed.
Riga et al. (Sat,) studied this question.