Isolation from predators: a key factor in the failed release of farmed red-legged partridges (Alectoris rufa) to the wild?

1. The effects of predation isolation were studied in two lines of 10 month-old farmed red-legged partridges (Alectoris rufa). Birds came from bred generations in captivity (F) and directly from wild parents (W). 2. Releases were carried out in March for two consecutive years on private farmland with a stable population of wild red-legged partridge using 68 tagged birds (36 F, 32 W). 3. No statistical differences were found in survival time (mean 18 d) or home range values (mean 7·38 ha); 49% of mortality was attributable to raptors, 36% to wild canids and 15% had doubtful causes of death. F birds suffered more predation by raptors and W partridges more by mammalian carnivores. 4. A statistical difference was found in post-release dispersion: the means were 243·4 m in F and 593·3 m in W. 5. The result of predation isolation was similar in both groups, which confirms the adverse effects of current production systems on anti-predator behaviour. Farmers should consider the introduction of new rearing techniques with the aim of improving survival after release.