In an age of rewilding and dramatic declines in biodiversity, we are developing a new way to reintroduce raptors: parental hacking. The principle behind it is similar to that which informs traditional hacking, where the birds are released without contact with adult conspecifics. In parental hacking, our method, the parents feed their own offspring until the end of the post-fledgling dependency period. Our programme aims to reintroduce the white-tailed sea eagle (Haliaeetus albicilla) to the Upper Rhône Basin in France. It started in 2022 and will continue until 2030, with the release of 80 young eagles. We describe the method used in 2022, followed by the improvements made in 2023, and finally compare the two years. The young eagles were raised in aviaries at the reintroduction site by their captive-born parents in the Aigles du Léman Park (Haute-Savoie, France). In 2022, two young females and two young males were released as soon as they were able to fly at the age of three months, but they often ended up on the ground due to a lack of flying ability and attacks from wild black kites (Milvus migrans) defending their territory. Therefore, the young eagles were returned to their parents’ aviary before being released a second time at five months in August 2022. One month after release, one male was already 50 km from the reintroduction site, while the other three stayed close to the park. In 2023, five young females and five young males were released at five months. This came after four weeks in a large training aviary to learn how to fly, perch, and fish. The behaviour of the young eagles one month after release varied greatly between individuals. Overall, 4 out of 10 young eagles travelled long distances and did not return to the reintroduction site to feed within a month, while the other 6 chose to stay close (within 20 km) to the reintroduction site.
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