Hen Harriers: not very good at being – er, Hen Harriers?

Next week I’m interviewing the RSPB’s Dr Cathleen Thomas, Senior Project Manager of the EU-backed Hen Harrier Life Project. Launched in 2014 the project is nearing completion, and Cathleen has been a remarkably passionate spokesperson for Hen Harriers, a declining bird of prey that in the UK is now restricted to a handful of mainly upland moorland sites.

The LIFE project specifically aimed to “provide the conditions in which the Hen Harrier’s population and range could recover, particularly in areas where the species was most threatened“. Over five years the project team protected over one hundred nests, monitored winter roost sites, satellite-tagged over one hundred birds, produced over fifty press-releases, and engaged with the public to spread awareness of the species amongst everyone from school children to the police and politicians.

But Hen Harriers have just kept on declining. In fact, between 2004 and 2016 across the UK and Isle of Man the population declined by 24%, with just 575 pairs of birds remaining. Which is odd when scientific estimates suggest there is sufficient habitat and food availability to support a population of over 2,650 pairs.


What’s going on?

Maybe Hen Harriers are simply not very good at being Hen Harriers? Maybe the evolutionary adaptations to the harsh conditions, the specialised feeding rituals to lessen the chances of ground-based predators like foxes finding nests, the cryptic plumages, the non-specific diet which means these birds will eat almost anything they can catch…just don’t work?

Maybe they are getting lost, flying into caves or down holes and not getting out again. Maybe they’re lazy, stupid birds that just don’t want to be Hen Harriers. Maybe Hen Harriers secretly want to be swans and go live on a pond rather than a heather-clad peat bog?


Or maybe it’s something else?

Could it be instead that, as the project reports, “a growing body of independent scientific evidence shows the main cause …is illegal persecution. In a recent study, 72% of tagged hen harriers were confirmed or considered likely to have been illegally killed, and this was ten times more likely to occur over areas of land managed for grouse shooting relative to other land uses“?

It’s certainly pertinent to ask, given that the RSPB has just had to put out yet another appeal for information for yet another missing Hen Harrier. Ada, as she was named, hatched on a nest on the Scottish borders this summer and is believed to have disappeared in one of the most notorious raptor crime hot-spots in the UK: the North Pennines Area of Outstanding Natural Beauty.


Survival Challenges

Ada was fitted with a lightweight satellite tag, as part of the very same Hen Harrier LIFE project described above, to learn more about the journeys made by these rare birds of prey and the survival challenges they face.

Could the satellite-tag simply have failed though (as shooting lobbyists usually claim)? As the hugely respected blog Raptor Persecution UK says today, “The tag Ada was carrying is believed to be the same make and model as the other tags deployed by the RSPB on Hen Harriers (the tag with a known reliability rate of 94%). Technical failures are possible (of course) but are rare (6%), and according to this research tag failures have always been preceded by irregular transmission periods and, most importantly, a drop in battery voltage (another parameter monitored by the transmitter). This makes it relatively straightforward to distinguish between a likely mortality event and a likely transmitter failure”.

A tag failure seems highly unlikely then.

Dr Thomas herself is quoted in the RSPB’s appeal for information. She says that, “Over 30 chicks were tagged this summer and we’ve watched with interest as they’ve grown up and flown around the country. We’re absolutely gutted that Ada has disappeared in suspicious circumstances at just a few months’ old.

A pattern of wildlife crime

Ada isn’t the first young Hen Harrier from the Project to ‘disappear in suspicious circumstances’ (which is surely shorthand for ‘We know what you did, but we can’t prove it.’) Six were either confirmed or suspected to have been illegally killed in 2016. Twelve were either confirmed or suspected to have been illegally killed in 2017, including Rannoch whose remains were found by RSPB Scotland caught in an illegally-set spring trap (image below) And in 2018 another twelve were either confirmed or suspected to have been illegally killed.

Ada isn’t the first by a long chalk, she’s just the first so far this autumn.

Not good at being Hen Harriers?

Dr Thomas and I are going to have a lot to talk about, but I think we can safely rule out one thing right now. The decline of the UK population of Hen Harriers has absolutely nothing to do with them not being very good at being Hen Harriers. Hen Harriers would actually be really, really good at being Hen Harriers – if only the shooting industry and moor owners would let them…