Breeding records and the detection of nesting predators of wild-release red-crowned cranes into non-breeding areas of the Yancheng National Nature Reserve, China

The western population of the red-crowned crane Grus japonensis in mainland China has been decreasing in the past few decades and wild population enhancement programmes have been launched in this country. First, 14 captive-bred red-crowned cranes were released into the core area of Yancheng National Nature Reserve for Rare Birds (YNNR), one of the most important wintering areas of this species, in 2013 (seven individuals) and 2015 (seven individuals) and then 8 more captive-bred cranes were released into YNNR from February 2022 to February 2023. We used satellite positioning and drone monitoring to study the status of released cranes. The results showed that two individuals (No. BJZ001 and BJZ008) from the first group of released cranes were found breeding in 6 of 7 years in the YNNR from 2017 to 2023. Three individuals (No. WNNR022, WNNR025 and WNNR026) from the second group of released cranes were recorded breeding in YNNR in 2023. All released cranes lived in the YNNR year round and did not migrate with wild cranes. Raccoon dogs, Nyctereutes procyonoides, were first recorded as red-crowned crane nest predators in the YNNR. Although these released cranes breed successfully in the YNNR, nestlings might face the threat of predators in non-traditional breeding areas. Further research is needed to determine whether offsprings of released individuals migrate with wild cranes and if breeding in their original wintering grounds is truly beneficial for population growth.