The four-year independent study, commissioned by Severn Trent Water and carried out the Lake Vyrnwy nature reserve in north Wales, was compiled with the assistance of the Game Conservancy Trust (GCT) and measured the survival and reproductive success of 39 fully grown black grouse.

The black grouse were radio tagged during the research period, and at the end of the study, only one was found to be alive.

It is thought that of the black grouse that were killed, 64% were killed by raptors (such as goshawk and peregrine) and 36 per cent by red foxes.

Dr David Baines, director of uplands research at the GCT, said, “We are particularly concerned about the Welsh black grouse population, which may once again be declining following a brief period of recovery. We predict that fewer than 200 males now remain. Severn Trent Water has invested heavily in black grouse recovery and so they initiated this important research to identify the reasons for these declines before it is too late.”

Over the past 100 years the population of black grouse has fallen sharply across western Europe and in some areas it has become extinct.