The open-access paper by Megan Murgatroyd, Stephen Redpath, Stephen Murphy, David Douglas, Richard Saunders and Arjun Amar is entitled:
Patterns of satellite tagged hen harrier disappearances suggest widespread illegal killing on British grouse moors.
This paper confirms what has become blindingly obvious to all, except to Defra ministers, over the years, that Hen Harriers are killed on grouse moors. and this is summed up in the paper thus;
Using data from 58 satellite tracked hen harriers, we show high rates of unexpected tag failure and low first year survival compared to other harrier populations. The likelihood of harriers dying or disappearing increased as their use of grouse moors increased.https://www.nature.com/articles/s41467-019-09044-w
We almost knew this from the dataset eventually published of last fixes of satellite-tagged Hen Harriers last summer. That dataset showed that lots of Hen Harriers’ die in their first year, indeed first few weeks of life and that they are often found dead or simply unexpectedly cease transmitting signals on driven grouse moors.
Why do I say ‘almost’? Let us imagine that a third of people die in bed – if we spent only 1% of our lives in bed then this would indicate that bed seems to be a pretty dangerous place but if we all get a good 8 hours a day asleep then we would expect that about a third of us would die in bed. And by analogy we need to know how much time Hen Harriers spend on grouse moors to assess their likelihood of death/disappearance on grouse moors compared with other land uses. If Hen Harriers spend all their time on grouse moors then a high proportion of them will die/disappear on grouse moors.
So we have to know about the relative time that Hen Harriers spend on and off grouse moors in order to analyse properly their risk of death/disappearance on grouse moors. This is an important finding;
… the mean percentage of [satellite] fixes on grouse moors per weekhttps://www.nature.com/articles/s41467-019-09044-w
for harriers that survived was (±SE) 15 ± 2.6 %, which was half of
the mean percentage for those which died or disappeared (30 ±
In other words, those Hen Harriers that died/disappeared spent 30% of their time on grouse moors whereas those that survived spent 15% of their time on grouse moors. If people who died spent twice as much time in bed as those who survived then you’d think twice about going to bed…
But the authors take this much further, and I admire the cleverness of the analysis. They look also at the use of different habitats by the Hen Harriers who were known to have been illegally killed or which disappeared unexpectedly (SNM – ‘stopped no malfunction’ where the transmitter stopped abruptly and unexpectedly based on diagnostic plots and the bird
was never found). The authors found that …
Harriers were more likely to be located on grouse moors duringhttps://www.nature.com/articles/s41467-019-09044-w
the terminal week (i.e. the last 7 days of tracking prior to the date
of death or disappearance) than during other weeks (Fig. 1a).
Moreover, the probability of a bird dying or disappearing
increased with the proportion of fixes on grouse moors …. and this pattern was more pronounced when only data from tracked birds that
were known to have been illegally killed and those with tags that
were classed as SNM were tested (Fig. 1b.
If you are a satellite-tagged Hen Harrier who has died, then you are very likely to have spent more time on grouse moors in your last week of life than on grouse moors in your previous weeks of life. Hen Harriers that spend lots of time on grouse moors face a much greater risk of death/disappearance thn those who do not.
But there is more …
Fixes from the terminal week were distributed disproportionately on grouse moors compared to their overall use (Supplementary Fig. 2). The proportion of fixes in each 20 × 20 km2 grid square, attributed to terminal weeks varied from 0.02 in grid squares with no grouse moors to 0.20 in squares with 50% grouse moor, indicating that harriers were ten times more likely to die (I and N) or disappear (SNM) in areas dominated by grouse moors (Fig. 2).
Ten times more likely… We’ve never seen that figure before and it can only come out of a dataset like this one with satellite fixes. Just remember we are always being told that Hen Harriers need grouse moors, love grouse moors and thrive on grouse moors – except that the science shows that they are ten times more likely to disappear or die on grouse moors.
You could say that the analysis in the paper so far has told us what we already knew, and to an extent it has, but is no less valuable for doing that so clearly and with data. We’ve known that Hen Harriers die on grouse moors with alarming frequency but this paper quanitifies, very importantly, how much more likely Hen Harriers are to die on grouse moors than in other areas – ten times more likely. Massively more likely.
But there is more, and this is really new.
The authors look at eight protected areas, so-called National Parks (NPs, which aren’t what anyone elsewhere in the world would call a National Park) and Areas of Outstanding Natural Beauty (AONBs). The eight areas are; Lake District NP, Northumberland NP, North York Moors NP, Yorkshire Dales NP, Peak District NP, Forest of Bowland AONB, North Pennines AONB and Nidderdale AONB.
Of these eight areas the Lake District has the lowest coverage of grouse moors in its boundaries (about 12%) and the North York Moors the highest proportion (about 30%).
The authors looked at the fixes from satellite-tagged Hen Harriers in each of these geographic areas and then for each area calculated simply the percentage of all fixes that came from Hen Harriers in their last week of life (or prior to unexpected disppearance). So this is not a measure of use of an area, it is a measure of the ratio of ‘fixes in the week you died’ to ‘flying around alive fixes’ and is therefore a measure of risk of death/disappearance in an area. And we’ve never seen that before.
The authors find that …
As the percentage area of grouse moor within a Protected Area (PA)https://www.nature.com/articles/s41467-019-09044-w
increased, there was an increase in the proportion of terminal
fixes per PA … This suggested that harriers were more
likely to be illegally killed in PAs that had more grouse moor
habitat. For those birds that were illegally killed or disappeared,
the North York Moors and the Peak District followed by the
North Pennines, Nidderdale, Yorkshire Dales and Forest of
Bowland had the highest proportion of terminal fixes, indicating
higher than expected harrier mortality in relation to use (Fig. 4).
So, the Lake District and Northumberland NPs are relatively safe places for Hen Harriers to visit. They may or may not be the greatest places to be if you are a Hen Harrier in terms of finding food etc but you are unlikely to be bumped off, or even simply to die, while you are flying around the Lake District NP. And these are the two NPs/AONBs with the smallest proportions of grouse moor within their boundaries. In the middle ground, as it were, in the Yorkshire Dales NP, where the simple maps of locations of dead Hen Harriers might lead one to think that this is the most dangerous place on Earth for this species, Hen Harriers spend quite a lot of time flying around alive too (not enough, but quite a lot). A middling proportion of fixes recorded within this NP come from the terminal week of life of Hen Harriers – and the Yorkshire Dales NP has a middling amount of grouse moor within its boundaries.
But the NP/AONB with the highest risk factor is, perhaps surprisingly, the North York Moors NP which, surprise, surprise, has the highest proportion of grouse moor within its boundary of all eight of the Protected Areas examined in this study.
Per day of flying around NPs and AONBs, Hen Harriers risk a higher chance of death in the North York Moors NP than any other (and it is the most dominated by grouse moor) and face the lowest risk of death per day in the Lake District NP and Northumberland NP (which have the lowest proportions of grouse moors within their boundaries). This finding is new and important.
This study is a devastating critique of the industry of driven grouse shooting. We are here only looking at the fate of free-flying young birds followed by satellite telemetry. We already know that grouse moors rarely host nesting Hen Harriers and that when they do the nests are likely to fail and the adults prone to die. But this analysis nails the lie of ‘a few bad apples’.
A Hen Harrier flying around the north of England risks death if it visits a grouse moor. The more time it spends on grouse moors the greater its chance of death. The more grouse moor there is in the area it frequents the greater the chance of death. The bad apples are distributed widely and in proportion to grouse moor abundance. And there are more than enough bad apples to drive the Hen Harrier population to close to be extirpated from the whole of northern England as a breeding species.
When you meet a grouse moor owner or upland game keeper you meet an individual from a so-called sport which is steeped, drenched, drowning in wildlife crime.
It’s likely that this blog will come back to this subject fairly soon…