The Hen Harrier – some biology

Photo: Tim Melling
Photo: Tim Melling

There is a lot of nonsense talked about the Hen Harrier -and about everything else in the world I guess.  Let’s hope I am not going to add to it.

Here’s my take on the biology of the bird.

What they eat: Hen Harriers eat lots of things. The Langholm study showed that the density of Hen Harriers settling on a moorland was related to the numbers of small birds (esp meadow pipits) and voles that were present. HH are birds of early successional stages – that’s why young forestry plantations were so good for them – lots of pipits and voles.  Moors with a mixture of grass and heather have the highest Meadow Pipit densities – a bit of overgrazing encourages HH.

But once you have your HH (you lucky grouse moor owner) then they certainly eat Red Grouse – adults and, more especially, chicks.  If you have lots of HH then they will eat lots of Meadow Pipits, lots of voles (in vole years) and lots of Red Grouse too.  We don’t shoot pipits or voles but some people do shoot Red Grouse after 12 August – HH don’t wait until after 12 August.  HH can eat so many Red Grouse that the type of intensive shooting that is practised in the UK, and nowhere else in the world, can be no longer possible. That’s what Langholm showed and it might well be true in other places if HH were properly protected. So, the conflict between people who want to shoot Red Grouse and HH is a real one.

Where they live:  Hen Harriers and Northern Harriers are two races of the same species, and live right around these latitudes across Europe and Asia and North America.  They are quite widespread.  In the UK they mostly live in upland areas, and are found in England, Wales, Northern Ireland and Scotland.  The range has expanded and contracted over the years in response to the level of persecution by Man (which, in the olden days, of course, was legal).

You mainly see HH nesting in areas of heather moorland. Some areas of moorland are managed for driven grouse shooting, others are not.  The areas where grouse moor management is dominant (northern England, southern Scotland and eastern Scotland) have very few HH these days (there used to be lots more of them – indeed many of these areas were designated as being important for nature conservation partly on the basis of the (now absent) HH).

Numbers of HH have increased in areas where there is little or no grouse shooting and decreased in those where grouse shooting is widespread.

How they die: HH nest on the ground and are vulnerable to a range of ground predators taking their eggs or chicks – especially, probably, foxes.  It’s noticeable that HH are common on the Western Isles, Orkney etc where there aren’t any foxes (nor is there driven grouse shooting – both will play their part).

A study by the RSPB showed that nesting success per attempting female was much lower on grouse moors than other moors, and that (through wing-tagging) female survival was much lower on grouse moors than other moors.  The HH population of grouse moors would decline steeply without immigration from other areas (forestry plantations and other (non-grouse-shooting) moors).  One way of describing this is that grouse moors are a ‘sink’ and depend on other areas providing a source of recruiting birds.  Etheridge et al (1997). The effects of illegal killing and destruction of nests by humans on the population dynamics of the hen harrier in Scotland. Journal Applied Ecology 34: 1081-1105.

In a published RSPB study the conclusion was: ‘Even a generous assessment of the magnitude of a supposed beneficial effect of the control of foxes and other predators by moorland gamekeepers on hen harrier nest success indicated that its effect on the population trend of hen harriers would be small relative to the large negative effect of persecution of harriers on grouse moors.Green and Etheridge (1999) JAppl Ecol  36:472 – 483.

How they move around: HH move quite a distance from where they hatch to where they settle to breed. They, unlike eagles and buzzards, are good colonists of new areas. This is what you would expect from a bird of early successional stages  – you have to be a good colonist.  It’s also how HH found and occupied all those young forestry plantations of the 1970s and 1980s -they evolved to do that sort of thing.

HH also move around in the winter – what a pity that NE are still keeping secret their study of HH movements!

I am now going to use the ‘mashed potato and soup’ analogy. I first heard this in a talk given by a friend of mine, Kate Lessells, at an EGI student conference in the late 1970s or perhaps early 1980s. Kate wasn’t talking about HH but the analogy works here.

If you imagine a bowl of soup, then if you dip your spoon in and take out some soup, the level of the soup goes down everywhere.  Soup is a liquid, it flows into the hole you created.  Whereas, you can scoop out a spoonful of mashed potato and you leave a hole in the mashed potato surface. Some birds have populations more like mashed potato, others like soup.  Buzzards and House Sparrows are more like mashed potato – HH are much more like soup.

Because HHs move around a lot, their populations are more soup-like.  They do move around – wing-tagging and radio-tracking, and now satellite tagging shows that. A bird hatched in Perth recruited to Langholm (in the Borders) in the Langholm study (that’s from memory but I’m pretty sure I am right).

So, if you have people killing HH on grouse moors, which you do, and reducing their nesting success, which you do, then that’s why the grouse moors are a sink. New recruits keep turning up each spring, searching for a good place to nest having been hatched far away, and they get bumped off too.  If persecution is strong enough the whole population goes down.

In areas which are mostly free from grouse shooting HH numbers are stable or rising (they don’t need to be cuddled by ‘keepers).  These areas are: Wales, Northern Ireland, Isle of Man, Western Isles, Orkney and the northwest Highlands of Scotland.  in those areas where grouse shooting predominates, northern England, south and west Scotland, east Scotland, HH numbers have declined.

But this biology also explains why it’s so difficult to protect HH in areas where there is a lot of grouse shooting – the birds move around in the winter, and from where they are hatched to where they breed, they have to be lucky not to get bumped off somewhere. Rumour, although it’s a bit more than rumour, has it that a favoured form of HH-killing these days is to bump off the birds at winter roosts.  I wonder what those satellite tagged HHs might show?

Have a look at Fielding, A., Haworth, P., Whitfield, P., McLeod, D. and Riley, H. (2011). A Conservation Framework for Hen Harriers in the United Kingdom. JNCC Report No.441, Peterborough.

 

Driven grouse shooting has been around for c150 years; Hen Harriers have owned our hills for rather longer.

The conflict between an economic activity of trivial value to the economy, which is also a ‘sport’, and a protected bird, protected in law for 60 years today, is a real conflict.  Hen Harriers eat grouse that paying shooters want to kill.

Hen Harriers might spoil some people’s ‘sport’ – grouse shooters are wiping out a protected species.

A wonderful bird or a bunch of armed criminals – whose side are you on?

Please sign this e-petition to call for an end to driven grouse shooting.

 

Tomorrow – 10 reasons to sign this e-petition.

 

 

 

 

 

 

 

 

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8 Replies to “The Hen Harrier – some biology”

  1. Another good piece Mark, I hope you plan another on grouse shooting being "an economic activity of trivial value to the economy". For the moors areas in question surely the issue is not whether there is some economic benefit from grouse shooting, which I suppose there may be, but rather whether other uses could generate more, which seems to me to be probable. In other words, if I remember the lingo right, it is the opportunity cost which matters. As well as hen harriers of course.

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  2. I had the rare pleasure of spending two summers observing hen harriers at their nest via CCTV link, courtesy of the RSPB, Clyde Muirshiel Regional Park, the SOC and SNH. While the purpose was to share this rare sight with the public, we also made careful notes of everything we observed at the nest - including prey species. Despite not always being able to see exactly what was going on, the records still gave us a good impression of patterns.
    In the two nests we followed, the vast majority of prey was meadow pipits - from memory these made up over 90% of prey. They also brought in a range of other small birds and only a few mammals (it was a 'bust' time for voles in the area). Once they brought in a stoat, which was an interesting clip to show the local keepers! Once, and only once, they brought back a chick which may have been a grouse. To be absolutely fair, the area was pretty poor as far as grouse moors go, but it was/is still managed in part for shooting. Still - ONLY ONE in two seasons!
    We also caught some incredible footage of a fox raiding the nest and taking four of the five chicks. It was no surprise that the very same people who would like to be able to 'control' the hen harriers were up in arms calling for better 'control' of foxes.
    These are incredible birds - amazing hunters, beautiful acrobats, and tender parents. They are not the grouse-eating maniacs that some would paint them to be, and even if they were - so what? Grouse are held at artificially high numbers, can you blame any predator that takes advantage of that?
    The thought that my own toddler son may grow up in a Britain without hen harriers is galling to me. Who has the right to take from him, and everyone, the chance of seeing a skydancing bluesleev'd harrier?
    We must - MUST - protect these birds at all costs.

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