The Hen Harrier Brood Management Trial was undertaken in England between 2018 and 2024 to assess whether brood management could contribute to hen harrier recovery by reducing conflict between hen harriers and driven grouse shooting. This evaluation combined data from brood management operations, nest monitoring, satellite-tagged birds, wildlife crime investigations, population modelling, and two social science studies of moorland managers (see related records).
Fifteen broods of hen harriers were taken from grouse moors, reared in captivity, and re-released. During this trial, numbers of wild nesting hen harriers in England increased substantially, with the strongest increases occurring on grouse moors where brood management was available. Population modelling indicated that this increase could not be explained by the direct productivity benefits of captive rearing alone, and was more consistent with improvements in survival and/or settlement rates of wild birds. However, illegal killing of hen harriers continued throughout the trial.
The trial suggests that availability of brood management led to more hen harriers successfully breeding on grouse moors. These increases in hen harrier nesting numbers appear likely to have been due to a reduction in illegal activity in some areas. However, illegal killing remains a significant constraint on recovery, and the trial did not demonstrate a widespread reduction in this. Future recovery is likely to require a combination of cooperative management approaches, monitoring, enforcement and surveillance tailored to local circumstances.