Support to the Black Grouse population reinforcement in Belgium: Report on the 2021 restocking operation of the last Belgian breeding population of Black Grouse in the Hautes Fagnes Nature Reserve, within the Hautes Fagnes (High Fens) Natural Park.

In the continuity of 2020, 2021 has been deeply affected by the human health crisis COVID-19. As a consequence, the catching/translocation mission in Sweden has again to be cancelled. No new Black Grouses were thus translocated two consecutive years, despite the authorization granted for 2*35 new individuals in springs 2020 and 2021. Additionally, we lost all the signal of the last tracked individuals since July 2020. The consequence is that this year 2021, data on the survival and breeding success were very poor. Several males translocated in 2019 are always very active on arena in 2021. Unexpected, a female from the first translocation 2017 was also observed this spring, after close to 5 years in Hautes Fagnes. Contrarily to 2019, it seems that the breeding success in 2020 and 2021 were not important, probably due to two successive humid spring/summer during the sensitive period of the hatching and the first weeks of the chicklings. The important increase of the population size between 2019 and 2020 (from 5 to 12 males) is followed by a slight decrease of this population between 2020 and 2021 (10 males). The population resists relatively well to the first year without reinforcement despite probably a weak recruitment rate by reproduction in 2020. The state of the population at the end of 2021 is unclear. Although data from the last fall count would suggest that population numbers were falling, we believe that the census' late date relative to the fall arena activity period underestimated the actual numbers. Only next year's spring census will allow us to highlight the real impact of this second year without reinforcement. However, we hope that the 2022 & 2023 missions will be carried out in helping us reach, as fast as possible, our objectives of population restoration in the Hautes Fagnes.