Paul Walton, Head of Species and Habitats for RSPB Scotland, brings us this blog on island life, the species that live there, the pressures they face and the work going on to protect them ahead of the World Island Invasives Conference which is taking place in Dundee next week.
Everyone knows what an island is – a piece of land surrounded by water. But actually defining the idea can be tricky, with the continents themselves surrounded ultimately by sea, some islands becoming joined to the mainland at low tides, whilst some others completely vanish at high tide.
The basic factor, though, is that an island is a place apart, a piece of land that stands alone, separated from the rest of the wider terrestrial environment. This condition means that life proceeds in relative isolation and, because of that, develops special, sometimes unique characteristics. Naturalists and biologists have appreciated this special nature of islands for centuries, and studying the wildlife of islands has revealed many truths about the wider nature of life on our planet - most notably, of course, following Charles Darwin’s seminal visit to the Galapagos archipelago in 1835.
When it comes to the conservation of nature, that specialness reaches new heights. Islands occupy only about 5.5% of the world’s land area, but contain more than 15% of all terrestrial species, 61% of all recently extinct species, and 37% of all critically endangered species. Understanding this, and tackling the issues facing island wildlife, are thus essential elements of our collective responsibility towards the natural world.
One critical part of island ecology is that species living on islands are often freed from the pressures of many of the competitors, diseases and, in particular, predators, that they would face if they were living on continents. For instance, most of the world’s 346 species of seabirds nest in colonies, on islands – known as seabird islands - and most of these species are heavily dependent on predator-free islands as breeding sites.
When people, accidentally or deliberately, introduce non-native predatory animals – principally rats, cats, snakes, stoats, ferrets and even mice - onto seabird islands, the effect can be devastating. Seabirds are the most threatened group of marine animals in the world, with around 29% of species classified as threatened – and most of these breed on islands. In Scotland, its thought that at least 13 colonies of the Manx shearwater alone, a beautiful bird of which around 40% of the world population breeds in Scotland, have been lost in recent centuries, mostly due to rat introductions to seabird islands.
Thankfully, there is much that can be done. First, we can take action to prevent the release of non-native species onto islands. This is called ‘island biosecurity’, and either prevents deliberate introductions (through education and awareness raising), or reduces accidental introductions from boats, transport and trade (through training, surveillance and trapping). Then, we can undertake projects that remove invasive non-native species that have already been introduced to islands by people – called ‘island restoration’ projects. Together, these measures can protect and restore island wildlife, with spectacular results.
About 80% of islands in the UK are in Scotland. These islands support globally important seabird breeding populations, and those populations are in trouble. One of the main causes is deep and fundamental shifts in the marine food-chain driven by human-induced climate change. Recent decades have seen the biomass of key zooplankton species plummet by more than 70% in the NE Atlantic. Climate change is warming the sea surface and this is generating asynchrony in the timing of zooplankton breeding, and the timing of the annual phytoplankton bloom on which they graze.
The system is out of seasonal synchrony and, to compound this, nutrient-poor warm water plankton species are beginning to replace the nutritious cold water species. The zooplankton is food for the key seabird prey fish - sandeels – and fewer sandeels is the result, with inevitable knock-on effects on the breeding success and survival of their predators, the seabirds.
The effect is patchy and varies between years – but the recent decades have seen more poor food years for seabirds than previously, indicating a long term shift in our seabirds’ core prey-base. Seabird breeding is failing, particularly in Shetland and Orkney where, for example, kittiwakes have declined by over 90% in recent decades. And many of the seabirds that do breed are now having to travel record distances to find prey to feed their young.
Faced with a shifting and diminishing food supply, and the intractable nature of climate issues, what can we do for Scotland’s seabirds? The answer is we can protect and restore as many island breeding sites as possible. This is essential climate change adaptation for our precious wildlife. By maximising seabird breeding opportunities around our coasts, we are giving these birds the best possible chance to exploit the food that is present. We thus build resilience in our globally significant seabird populations to the challenges we know they will face in future.
This month, the University of Dundee is hosting the World Island Invasives Conference, 2017. This event will bring together the world’s expert academics, practitioners, ecologists and officials to share experiences of island restoration and biosecurity. Dundee University staff have been leading the rat eradication on South Georgia, perhaps the world’s most important seabird colony and one of the most challenging island restoration projects ever attempted.
It is a hugely timely and exciting event, which will, I hope, signal the beginning of a step-change in island biosecurity and restoration work in Scotland, other parts of the UK, the UK Overseas Territories and around the world, learning from past experience and building on best practice. Let’s hope that by coming together, people can work meaningfully and constructively to protect island wildlife from the huge pressures we, collectively, have placed upon it.
New research has just been released which maps out the most important areas for Britain and Ireland's seabirds when they go out to sea to feed, with the majority of the 'hotspots' being found off the coast of Scotland. Rich Howells, from the marine team at RSPB Scotland, brings us this latest blog explaining a bit more about the research and what it means for seabird conservation.
Photo credit: Gary Howells.
A razorbill launches out to sea, but where is it going?
There are many things we know about Scotland’s seabirds: we know a guillemot found on Canna in 2016 was 38 years old, making it the UK’s oldest known seabird; we know gannets breeding on Bass Rock can travel a huge 540km in a single foraging trip to find food; and we know shags at Sumburgh Head dive to an impressive 61m in pursuit of their prey. We also know from long term studies that many seabird populations are declining, in some instances rapidly, due to a combination of factors including climate change, over-fishing and introduced predators.
Surveys from aeroplanes and boats have given us a good idea of where seabirds go at sea when they travel from the breeding colony to find food. Indeed this knowledge has allowed the identification of areas that qualify as Special Protected Areas (SPAs) under the EU Birds Directive. However, a gap free picture, allowing us to assess exactly where birds go and just how important areas of sea are for seabirds would need us to track individual birds from every single colony in Britain and Ireland, not an easy task with over 3,000 colonies hosting somewhere in the region of eight million birds of 25 different seabird species. But is there another way?
Sandeel is the main prey of many seabirds in Scotland. Photo credit: Steve Garvie.
In a landmark study and using a small team of expert bird catchers, RSPB scientists, working with researchers from institutes and organisations across Britain and Ireland, combined GPS tracking and mathematical modelling to identify the foraging areas that are most used by Britain and Ireland’s breeding seabirds, and found that the majority are concentrated around the coasts of Scotland.
Seabirds are among the fastest declining group of birds globally. Although our shores host internationally significant populations, breeding seabird numbers have fallen by 22% across the UK over the last 30 years. Declines are most severe in Scotland where breeding numbers in 2015 were 50% down on the 1986 level, when reporting began. This new research has important implications for the protection of seabirds, as without this kind of knowledge it is extremely difficult to reliably assess the impacts of developments, fisheries or other human activities on their breeding colonies.
Although much scientific attention has been paid to seabirds during breeding (for example see here), this has been predominantly focused on the nest, where birds are relatively easy to monitor. Until recently, studying seabirds away from their breeding sites involved observing birds from boats and planes. This provided a snapshot of where seabirds fed, but it was usually impossible to identify which colonies these birds had come from.
Traditionally, seabird studies were restricted to monitoring birds at their nests, or from boats and planes at sea. Photo credit: Gary Howells.
Recent advances in tracking technologies have miniaturised data-loggers to the point that they can be safely attached to the backs or tails of seabirds, allowing us to follow their foraging movements while out on the open ocean. By studying more than 1,300 adult birds from 29 different colonies, scientists were able to use this approach to track the foraging movements of four seabird species: shags, kittiwakes, guillemots and razorbills.
A kittiwake wearing a GPS tag on its back.
The inaccessibility of many seabird colonies further limits our understanding of seabird populations at a national level, and even where colonies are accessible, not all can be monitored. Remarkably, using what the tracking revealed about where birds go, the authors were able to model the foraging distributions of seabirds at colonies where individuals had not been tracked; a gap free picture emerges, predicting where these species go from more than 5,500 breeding sites around Britain and Ireland.
Predicted use of marine environment by four UK seabirds.
This new information allows us to assess the potential impacts of activities around our shores on seabirds, such as offshore renewable developments and different types of fisheries. It could also help in identifying colonies most at risk from specific threats like oil spills. Crucially, by identifying the areas used most intensively by foraging seabirds, conservationists and policy makers can more accurately identify sensitive areas for seabirds which will be relevant for the designation of Marine Protected Areas and marine spatial planning.
This is the third post in a six part blog series about rare insects in the Cairngorms. A new project launched this year to save six endangered invertebrates in the north of Scotland and project officer Gabrielle Flinn will take a closer look at one of these species each month. This time, it's the turn of the northern silver stiletto fly. The Rare Invertebrates in the Cairngorms project is a partnership involving RSPB Scotland, the Cairngorms National Park Authority (CNPA), Buglife Scotland, Butterfly Conservation Scotland and Scottish Natural Heritage (SNH).
Soaring into the air about two to three metres from the ground and flashing its reflective body, the northern silver stiletto fly (Spiriverpa lunulata) suddenly drops to the floor again. Males will do this, flying up and dropping again, several times before ascending into a full dance to try and attract the attention of a female.
If a female appears, the males will form 'leks' (much like some bird species, for example black grouse) to compete for her attention. Despite the allusion to high heeled shoes in its name it is not called the northern silver stiletto because of this performance. The abdomen of the fly is shaped like a stiletto knife and covered in silvery hairs to give it a shimmering appearance.
The fly survives on shingle - the sandy, rocky banks that can be found alongside and on rivers. It prefers slightly vegetated river shingle where it can shelter and feed as an adult. River shingle habitat can be impacted by annual flooding and so long-life banks that manage to withstand this flooding are of great importance as reliable sites to the fly.
River Shingle. Photo credit: Stephen Hewitt.
Amongst the sandy deposits, the eel-like larvae travel just below the surface searching for invertebrate prey to bite and destabilise with their venom before consumption. The venom is not dangerous to large animals such as humans, however, so there is nothing to fear whilst having your picnic by the Spey!
After enough feeding the larvae will pupate into an adult with June and July being the best time to see them. Females can be distinguished from males by their smaller eyes (as with all flies) but also by the black stripes on the abdomen between the silvery hairs.
During the training day that we ran this month, volunteers were lucky enough to find several larvae and observe the males starting to dance. Over the course of the Rare Invertebrates in the Cairngorms project we hope to better understand the distribution of this species so we can help to conserve it and the integral habitat on which it and many other invertebrates rely.
The first two blogs in this series focused on the shining guest ant and the Kentish glory moth. Give them a read by clicking the links.