British wildlife and fell running are two of my favourite things. I've always thought these interests fit hand in glove - with each deepening my appreciation of the other. But I recently found myself questioning whether my hill-running could be having an adverse impact on our precious upland wildlife.  Like most fell runners, I spend as much time as I can running around my local hills and mountains, usually on waymarked trails and paths, but often - particularly in races - taking the shortest line down off a hill along a sheep trod or through heather and bracken. Many hill-walkers too, like to take the road less travelled and there's much to discover and enjoy when we do. So what wildlife should we be considering, if out walking or running this spring?

I asked three local ecologists what wildlife we might sharing the hills with or be impacting, when out hillwalking or fellrunning in Wales' uplands: Andy Karran of Gwent Wildlife Trust, Chris Hatch, County bird recorder for Torfaen and George Tordoff, of the Butterfly Conservation Trust. Here’s what they told me.

Andy: My thoughts would be to minimise any adverse impact on wildlife, to keep to the actual path whilst out running, not the edges just off it, as this is often quite a nice area for flora and will lead to the path widening further. The other point to note is that some upland breeding birds are scarce and vulnerable to disturbance: species such as Curlew, Golden Plover, Hen Harrier. Although I suspect dogs off leads too, motorbike scramblers cause more of an issue for them than fell runners. Again, good choices are keeping to paths and race organisers being willing to re-route courses if it is flagged up them that a sensitive species is nesting close to the path. All of this would be far more of an issue during breeding season, so March – August.

Chris: Runners should keep to the path to avoid damaging the vegetation. The most sensitive time for ground nesting birds will be from late March until the end of July, so running through heather or grassland would have an impact at this time of the year. There is a real chance in mid and north Wales that Schedule 1 birds like Hen Harriers may be nesting in stands of heather: these birds are very sensitive to disturbance, so it is really  important that runners stick to paths. Also, running near quarries, rock faces etc., may disturb other Schedule 1 nesters like Peregrine Falcons. Running through heather etc, may disturb Adders, which could strike at participants or dogs if they are accompanying them. Running through heather also may result in ticks being picked up; again, either by humans or dogs. Running through bracken may result in bites from bracken mites. All in all, far better to stick to paths!

George: In South Wales an important species to mention is the Silurian Moth, which in the UK is only found in SE Wales (and just straying over the border into Herefordshire). The main populations are on Blorenge, Coity Mountain (between Abertillery and Blaenavon), and in the eastern part of the Black Mountains - Hatterrall Ridge and Darren Lwyd. It breeds on Bilberry moorland above 450m altitude, so could be sensitive to high footfall, though grazing pressure and climate change impacts are likely to be the main threats. There's also Welsh Clearwing which breeds in old birches at the upland fringe, the caterpillars living inside the trunks. The main areas in South Wales are the valleysides NW of Capel-y-ffin (close to where Silurian occurs) and further south in the Black Mountains around Llanthony and Mynydd Du forest. Though there are nice old birches further west in the Beacons it doesn't seem to occur there. In NW Wales it is a bit more widespread. It's not likely that runners will have any impact on this one, though it is quite an iconic upland fringe species in Wales and is threatened by lack of birch tree regeneration - so worth thinking about perhaps.
In North Wales there are two moths found nowhere else in the UK - Ashworth's Rustic and Weaver's Wave. These breed on rocky hills, often with a lot of scree. I don't imagine that runners will have any significant impact on these, but they are iconic Welsh moths so again, good to know they are there.
For butterflies, there are no especially rare species in the uplands of South Wales, though Small Pearl-bordered Fritillary does occur in small numbers across the Brecon Beacons National Park, and more widely in north and west Wales, breeding on streamsides and wet flushes. They could be sensitive to high footfall though again, overgrazing is a greater threat. Large Heath occurs on boggy moorland in North Wales - it's quite a rare butterfly breeding in large, flat areas of bog habitat (e.g. Migneint), not the kind of places where fell races tend to take place. Small Heath, a common but rapidly declining species, is the most abundant species at higher altitudes in Wales. I think overall impacts are likely to be greater for wildlife that is sensitive to disturbance, like breeding birds.

It's wonderful to know that when I'm out on the hills, these fascinating creatures might not be too far away. I'd hate to think I might disrupt their breeding and nesting in this important season so I for one will be keeping to the paths, at least til next winter.