Claim
Hen harriers are illegally killed on English grouse moors
What the science says
True.
The science supports this claim. Hen harriers were recently found to be ten times more likely to die or disappear in an area managed for grouse, and the scientists concluded that illegal killing was the most likely explanation. There are other important and largely unquantified reasons for harriers to die such as predation and weather, but illegal killing is thought to be the main factor preventing their recovery in England. The Defra hen harrier recovery plan aims to address the fear driving this practice and resolve the conflict.
From:
This was a widely reported story carried in many newspapers and on the BBC.
https://www.bbc.co.uk/news/science-environment-47629829
Based on:
A scientific paper published in 2019 by Murgatroyd and colleagues used radio tags to track hen harriers and the results suggest that illegal killing is widespread on grouse moors1.
The fuller picture:
Hen harriers, along with other birds of prey, have been long been perceived as a threat to human interests, either farming or game management. As a result of humans killing them, hen harriers were driven to extinction on mainland Britain by the end of the 19th century. Following protection, there has been a gradual recovery, which is most notable in Scotland as reflected by national hen harrier surveys2–4.
However, it is known that hen harriers can pose a threat to red grouse, and on moorland managed for grouse continued illegal killing is driven by the fear of harrier predation keeping grouse numbers too low for driven shooting5. Where conditions are good, many harriers can nest in a small area and pose a threat to grouse numbers. This has been confirmed by scientific studies carried out by the GWCT and partners at Langholm Moor in Scotland, where in the absence of illegal killing and where the moorland was managed for grouse the number of harriers increased ten-fold, from two to twenty in five years5. The fear of this situation still drives illegal hen harrier killing, despite legal protection for the species.
In 1997 the first scientific evidence was published that gamekeepers limit the numbers of hen harriers on grouse moors6, and in 1998 the GWCT’s Dick Potts published an estimate of the impact of this on the hen harrier population7.
Ongoing illegal killing in England was the conclusion from a paper published in 2019, presenting data up to 2016, which showed that hen harriers were ten times more likely to die or disappear in areas managed for grouse. Their final week of life was much more likely to be spent on a grouse moor than in other areas1. These results suggest that illegal killing is still likely to be ongoing on and around grouse moors.
The grouse moor effect
However, studies show that in the absence of illegal killing, grouse moors can provide good habitat for hen harriers. The habitat management which benefits grouse helps protect heather moorland, and predator control reduces predation on both red grouse and hen harrier nests and chicks8.
Noting this and seeking to address the probable illegal activity and the poor conservation status of hen harriers in England, in 2016 Defra published its Joint Action Plan to increase the English hen harrier population. It combines several approaches to supporting hen harrier recovery, notably reducing wildlife crime, introducing the species into new range and addressing the underlying cause of the illegal killing, being concern over predation impacts on grouse. There are indications that things may be beginning to improve for hen harriers. The past two years have seen increases in the number of nests in England, as well as chicks that have fledged. Well over half of these chicks were produced on grouse moors. The numbers remain very low, but the Defra plan is designed to address the underlying factor driving the conflict.
References
1. Murgatroyd, M., Redpath, S.M., Murphy, S.G., Douglas, D.J.T., Saunders, R. & Amar, A. (2019). Patterns of satellite tagged hen harrier disappearances suggest widespread illegal killing on British grouse moors. Nature Communications, 10:1094.
2. Hayhow, D.B., Eaton, M. a., Bladwell, S., Etheridge, B., Ewing, S.R., Ruddock, M., Saunders, R., Sharpe, C., Sim, I.M.W. & Stevenson, A. (2013). The status of the Hen Harrier, Circus cyaneus, in the UK and Isle of Man in 2010. Bird Study, 60:446–458.
3. Sim, I.M.W., Dillon, I.A., Eaton, M.A., Etheridge, B., Lindley, P., Riley, H., Saunders, R., Sharpe, C. & Tickner, M. (2007). Status of the Hen Harrier Circus cyaneus in the UK and Isle of Man in 2004, and a comparison with the 1988/89 and 1998 surveys. Bird Study, 54:256–267.
4. Wotton, S.R., Bladwell, S., Mattingley, W., Morris, N.G., Raw, D., Ruddock, M., Stevenson, A. & Eaton, M.A. (2018). Status of the Hen Harrier Circus cyaneus in the UK and Isle of Man in 2016. Bird Study, 65:145–160.
5. Redpath, S.M. & Thirgood, S.J. (1997). Birds of prey and red grouse. Stationary Office. London.
6. Etheridge, B., Summers, R.W. & Green, R.E. (1997). The Effects of Illegal Killing and Destruction of Nests by Humans on the Population Dynamics of the Hen Harrier Circus cyaneus in Scotland. The Journal of Applied Ecology, 34:1081–1105.
7. Potts, G. (1998). Global dispersion of nesting hen harriers Circus cyaneus; implications for grouse moors in the UK. Ibis, 140:76–88. 8.
8. Baines, D. & Richardson, M. (2013). Hen harriers on a Scottish grouse moor: Multiple factors predict breeding density and productivity. Journal of Applied Ecology, 50:1397–1405.