Harried to death

Every time that we mention that we believe that gamekeepers are encouraged to bump off hen harriers on grouse moors there is a predictable outcry from the Countryside Alliance, the Shooting Times, sometimes the National Gamekeepers Organisation and others.  They say there is no evidence to back this up and that hardly anyone has been successfully prosecuted for such offences.  We'd agree with the fact that there have been few prosecutions dealing with hen harriers (many more for other birds of prey of course) and that is a source of frustration for us.

But one of the advantages of having been around for a while, and paying attention to the science on the matter too, is that one can remember how things used to be.

Here is a quote from the summary of a scientific paper published in 1998:

'In the U.K., a full recovery of Hen Harrier Circus cyaneus breeding numbers is prevented by illegal culling by some gamekeepers who fear the species threatens the future of grouse moors. This study’s main purpose was to estimate how many more Hen Harriers there would be in the U.K. if this culling were to cease.'

Later in the summary, I've missed out some dull bits, the author states:

'If all potential habitats were occupied, present numbers could more than double, to an estimated 1660 nesting females. This estimate represents an average of one nesting female per 25 km2 of habitat, a density which would cause little or no significant economic damage on grouse moors.

'However, because Hen Harriers tend to aggregate, they would not spread out evenly but would nest in relatively high densities on a number of moors. The economic impact on Red Grouse Lagopus lagopus would not be a function of overall numbers, rather it would arise from the uneven dispersion of nesting Hen Harriers.'

And who was this author?  None other than Dick Potts, who was then the boss of the Game Conservancy Trust.  The paper was published in the journal Ibis Vol 140, pp 76-88.

The RSPB was active doing science on the subject around this time too.

Here is the complete summary of a 1997 paper entitled  'The effects of illegal killing and destruction of nests by humans on the population dynamics of hen harriers Circus cyaneus in Scotland in the Journal of Applied Ecology, Vol 34, pp 1081-1105 :

'1. Breeding productivity, natal dispersal and survival of hen harriers Circus cyaneus were studied between 1988 and 1995 on moorland managed for sport shooting of red grouse, other heather moorland and young conifer forests in the uplands of Scotland. 2. Nest success was much lower on grouse moors than on other land management classes. Annual productivity was 0.8 fledglings per breeding female year on grouse moors compared with 2.4 on other moorland and 1.4 in young conifer forests. Human interference was recorded on half of the grouse moor estates studied and accounted for at least 30% of breeding failures in this land management class. It was much less frequent in the other land management classes. 3. Annual survival of female hen harriers which bred on grouse moors was about half that of females breeding on other moorland. On grouse moors, survival of females which bred unsuccessfully was much lower than that of females which reared at least one fledgling. Survival of breeding females on other moorland was high and unrelated to breeding success. The difference in survival of breeding females between grouse moors and other moors was attributed to killing by humans. On average, 55-74 females were killed each year, 11-15% of the total population of breeding females in Scotland, excluding Orkney. 4. The population of breeding females on grouse moors was estimated to decline rapidly without immigration. Harriers breeding on the other habitats were producing a surplus of female recruits approximately sufficient to compensate for the losses on grouse moors. 5. Most females started to breed at 1 year old and most males at 2 years old. The percentage of breeding males which were 1 year old was higher on grouse moors than on the other land management classes. 6. The median natal dispersal distance of both sexes exceeded 10 km. Harriers fledged from one land management class were often found breeding in another. 7. Natal dispersal resulted in net movements of 1-year-old females between land management classes which were sufficient to reduce the differences in population trend which would otherwise have occurred. Moorland managed for grouse shooting was a sink habitat which received two-thirds of its female recruits from other habitats. 8. The difference in productivity and survival between grouse moors and other habitats was attributed to illegal human interference. It is speculated that, without persecution, the hen harrier population in Scotland would increase, initially by about 13% per year, until a new, but unknown, equilibrium level was reached.'.

There is more science to back up our claims too - but let's just talk about the issue now. 

This issue has dragged on for years and no party is blameless.  For example, we used to say, and we believed it when we said it, that hen harriers wouldn't do much damage to a grouse shoot.  The Langholm study which we helped to fund showed that that was not always the case.

But for those representing shooting interests to claim that there isn't any evidence for killing of hen harriers puts the argument back a few decades. 

The thing that has changed since the science was carried out is that there are now even fewer hen harriers on grouse moors - the study in Scotland probably couldn't be done these days there are too few birds - and hen harriers have recovered somewhat in the places where there isn't grouse shooting.