not-yet-known not-yet-known not-yet-known unknown Conclusions We identify two main grey partridge lineages within Europe, termed Eastern and Western. In the UK and Greece, the captive grey partridge used for release are mostly of Western heritage, however, the respective wild birds of each country are of differing ancestries, west and east respectively. Our results suggest there has been differing success of released birds in these two locations. In the UK the wild birds share mitochondrial similarities with the captive stocks, however, show very little introgression of the eastern lineage, considering it is present in UK captive stocks. In Greece, the success of released stock is even less evident, with very little evidence that any of the captive stock have bred successfully after release. Considering releases, using captive stock, have been ongoing for decades, these results highlight the need for considering the heritage of captive birds used in releases if the aim is to bolster populations for long-term conservation success. We advise that further research aims to test whether this finding is due to theĀ overall low success rate of released birds generally or outbreeding depression due to unique adaptations in the two lineages.