Hen Harriers make history on the Isle of Lewis

A conservationist's dream

It’s not often in conservation that we are able to report on the appearance of a new population of a scarce bird species. But, on the Isle of Lewis, Scotland’s largest island, hen harriers have established a breeding for the first time in recorded history. The hen harrier has long been one of my favourite birds so experiencing and documenting the arrival of breeding harriers near me has been particularly exciting. The hen harrier was once described to me as the enlightening element of a windswept moorland and this is the most fitting description for this elegant bird that seems most at home slicing through the breeze as it quarters low over the ground in search of prey. Males are particularly eye-catching with their pale grey plumage, black wing tips, and their undulating displays over prospective nesting areas on bright spring days are an unmistakable spectacle. Once breeding is underway, the male delivers prey to his partner through an aerial food pass with the more camouflaged female delivering the prey to the nest. In this way, the brightly coloured male avoids attracting unwanted attention to the nest.

However, in Scotland the hen harrier population has suffered from illegal persecution on grouse moors for many decades. Recent satellite tagging programmes have exposed the extent of this threat with a large proportion of tagged birds disappearing on grouse moors each year under suspicious circumstances. In Scotland, the breeding hen harrier population was estimated to be just 460 pairs in 2016 when the last survey was carried out, a decline of nine percent since 2010. The now precarious and declining status of harriers across Scotland makes their recent appearance on Lewis even more important and extends their breeding range to the north-west.

The first nest on Lewis was located in 2015 and in 2016 four nests were found. Surveys in 2019 located nine pairs and it is now estimated that there are over 10 pairs breeding on Lewis. Harriers can be illusive and although it is possible that isolated breeding attempts went un-noticed before 2015, the species was not a regular breeder and harrier sightings were rare.

The neighbouring islands of Uists have a healthy population of hen harriers and it had been thought that their absence from Lewis was due to a lack of voles, one of the hen harriers main prey species.  However, it is now thought that hen harriers have established on Lewis in response to changes in land management. Hen harriers usually nest in deep heather and are particularly attracted to young woodland plantations on moorland. Sheep numbers have decreased on Lewis over the last 20 years and as grazing pressure has dropped, heather has recovered providing nesting habitat for harriers and more habitat for prey species such as meadow pipits. The presence of some young plantations in moorland areas is also likely to have been attractive to harriers and added diversity to their habitat. We think these changes have enabled hen harriers to colonise, but more research is needed as we don’t yet know much about what this population is feeding on in the absence of voles.

As with many conservation stories, it’s not all good news for harriers on Lewis. The core area where the harriers have chosen to breed is the site of the proposed Stornoway Wind Farm, a large 35 turbine proposal which is currently at application stage.The RSPB has responded to this planning proposal with concerns that the wind farm poses a threat to the harriers both from collisions with turbines and disturbance from the construction and operation of this large development. We have asked for the removal of a number of turbines which are closest to the breeding and roosting sites of hen harriers and other sensitive species. This would mean that the renewable energy project could potentially go ahead while reducing the impacts on this new and fragile hen harrier population.