A record breaking giant tortoise in Cumbria

RSPB Scotland Research Assistant, Davide Scridel, has gone south this summer to search for ring ouzels in the North Pennines. Read on to find out more about his work with this elusive species.

A record breaking Giant Tortoise in Cumbria

Stunning view of RSPB Geltsdale reserve.

I must admit, my 2014 field season research location is not based in a bad location at all. Not only does it fall into an Area of Outstanding Natural Beauty, but it is also at the foot of giant tortoise! Appearing like a mirage at the south of the frenetic A69, you can just about make out its top shell. Today known as “Tortie hill” – in ancient times  known as “Tortoy”, “Tortise” inferring “tortoise-shape” - lies in the heart of RSPB Geltsdale reserve and there is no doubt that this hill conforms to the reptilian outline. The combination of blanket bog, heath, upland farmland, as well as ancient woodland and pasture, make this reserve a jewel of the North Pennines. Since my arrival at the beginning of April, I have had some of my best wildlife sightings and I must thank the weather for this. The recent mild climatic conditions (one of the mildest winter and spring periods in the UK records) is potentially responsible for the record-breaking counts of many bird species here at the reserve. So far historic record counts have been broken for the number of black grouse lekking males (55), whilst the high abundance of voles visible on site may have influenced the greatest number of short-eared (21) and long-eared owl territories (6) seen in Geltsdale for a long time. Important increases have also been observed for merlin (9), lapwing, redshank, cuckoo, dunlin (2), whinchat (80+) and stonechat (20 to 30) territories. The first record of a twite nest was also a great surprise this year given its national scarcity. 

Short eared owl.

Searching for Ring Ouzel

Male ring ouzel.

Despite being very easily distracted by the incredible bird diversity on site, I must remember the reason why I am here. I am spending spring and summer 2014 in Geltsdale to work on an exciting, innovative and ambitious project which aims to recover populations of a bird that many people might never have heard of, but which is a symbol of the British uplands and it is currently facing serious problems. The ring ouzel Turdus torquatus, or mountain blackbird, is the only summer visiting thrush in the UK, and just one of the several upland species undergoing a marked range contraction and population decline.  Since 1999 ring ouzels have been listed as a bird of High Conservation Concern in the UK.  Dr Innes Sim (RSPB Centre for Conservation Science) has been on this case for several years. Thanks to his and other scientists’ research, we think we have now pinned down the major reasons for the decline of Population declines appear to be primarily driven by low survival of juvenile birds. Improving the survival of first-year birds is therefore the target for potential conservation actions for this species in order to stabilise and reverse recent population declines.

Getting the Right Mix

Previous radio-tracking work in Scotland has helped to better understand ring ouzel habitat requirements. Ring ouzels not only like deep vegetation such as heather to hide their nest and fledglings, but they also require short grass-rich areas in which to forage for invertebrates (particularly earthworms). Prior to migration they also select sites rich in moorland berries (bilberry and crowberry) where birds can boost their energy reserves before departing for their wintering grounds in the Atlas Mountains of north-western Africa. Changes in grazing and moorland regimes have in fact varied historically and regionally across the UK, through the reduction of sheep numbers on the moors (causing the loss of invertebrate-rich, short-grazed, grassland), or through overgrazing which has reduced heather cover where Ring ouzels nest and shelter from predators.

Three Year Trial

Over the next three years - in a project jointly funded by Natural England and RSPB - we have the opportunity to apply direct conservation actions by providing this mix of habitats at two RSPB reserves: Geltsdale and Dove stone (just at the door-step of the Peak District National Park). These two reserves offer a suitable scenario to test and apply these first-ever conservation actions. Both reserves feature valleys where ring ouzel numbers have been stable in recent years (control), and have historically declined (treatment). At a first glance, the treatment valleys appear in line with above-mentioned hypotheses: overgrazing at Dove Stone has caused a reduction in heather cover, while in Geltsdale the disappearance of sheep has diminished the amount of grazed grass foraging habitat available. Therefore, at the treatment valley at Dove Stone, we will monitor vegetation composition and structure in an area where sheep have been excluded since 2008, with the hope that recovery in heather cover will be beneficial for ring ouzels. At the treatment valley at Geltsdale, we plan to re-introduce sheep grazing in autumn 2014 to try to re-create the short-grass foraging habitat favoured by ring ouzels. Through these actions, we hope to re-create the habitat mix found in the control valleys, and thus return the number of breeding ring ouzels in the treatment valleys to their historic levels.

My First 2014 Ouzel 

Photo of ring ouzel chicks by Mingaile Zebaite.

My first seasonal sighting of a ring ouzel in the treatment valley at Geltsdale was on the 18th of April. This male mate-guarded the female, whilst foraging for red holly berries. This was a new and exciting observation (I have never seen an ouzel feeding on Holly berries before!).  Ring ouzels can be a particularly tricky species to work with, and continuously challenge your birding skill confidence. This bird has a quite large body size (similar size to its cousin the blackbird) and the males have a very obvious bright white collar (the gorget) and an unmistakable wild, mellow and fluting song: trrü trrü  trrü  trrü … si-vütt si-vütt si-vütt si-vütt … chuvüü chuvüü chuvüü chuvüü … Despite these characteristics which should make the bird fairly obvious, if they are nesting, or just in a “weird mood” they can be incredibly elusive. Very occasionally they take long and high flights, sometimes more than 1km, from their territory just to forage in some lush grass, making themselves completely invisible even to the expert birder. Only repeated observations, lasting for several hours, from a variety of vantage points can ensure the presence or absence of this species in the area. At the beginning of April, Geltsdale also provided an insight into the behaviour of the ring ouzel that I have never experienced before. A common belief is that Ring ouzel can be outcompeted by other thrushes, in particular mistle thrushes. Given that Geltsdale reserve is quite close to houses and gardens, I was very impressed to observe a Ring ouzel feeding less than ten metres away from not only mistle thrushes, but also blackbirds. I later found an ouzel nest less than 50m away from that of a blackbird, and I have not yet experienced any signs of aggression between the two species. Overall, numbers of ring ouzels appear to be in line with previous years, with 13 territories occupied on the reserve, and the treatment and control valley having 0 and 3 breeding pairs respectively.

Flora survey

Emperor moth.

Vegetation monitoring relies on measuring composition and structure in both treatment and control valleys. It is a particularly important part of the job to keep recording changes in vegetation not just over one season, but also throughout the three years of work. Despite its importance, keeping your head down for 8 hours a day between one quadrant and the next can sometimes be “challenging”. Luckily there are plenty of adders, emperor moths and green hairstreak butterflies to keep me awake and entertained! Almost in time with the first signs of bilberry ripening, the first broods of the typically double-brooded ring ouzel have already fledged, and the emerging bracken, together with some thick heather, are forming a perfect cover for the food-demanding juvenile birds. Some males are already singing again in the Geltsdale reserve, ready to set up new territories for the second broods. I hope in the next few months to get even more new insights from this charming, yet mysterious, bird.

Adder 

Many thanks to Adam Moan for the help during fieldwork.