Blog post by Nick Wilkinson, Conservation Scientist, RSPB Centre for Conservation Science
The twite is a little known small seed-eating finch, the upland cousin of the more familiar linnet. In the UK, twites breed predominantly in coastal areas of northwest Scotland, with much smaller populations in England, Wales and Northern Ireland.
They nest mainly on moorlands and along sea cliffs and feed in flower-rich habitats, often in adjacent farmland.
The twite is red-listed in the UK owing to a long-term population decline, so we conduct periodic national surveys in order to update our knowledge on their numbers and distribution (as we do for a range of species, e.g. capercaillie, golden eagle and ring ouzel).
These surveys are conducted in partnership between national Government conservation agencies and the RSPB under the Statutory Conservation Agency and RSPB Annual Breeding Bird Scheme (or SCARABBS for short).
Results from the second national survey of twite, carried out in 2013, are published today in the journal Bird Study and indicate a further decline in the UK population.
A team of surveyors made counts of twites across a randomly selected sample of 1km grid squares throughout the species’ range in England, Scotland and Wales, while a complete census was made in Northern Ireland.
Each square was surveyed three times between May and July by surveyors walking transects and making five minute stops to scan and listen for birds in suitable nesting habitat. This was the same method as used for the first national survey in 1999.
Extrapolation of the counts on surveyed squares to the area of the range not surveyed gave a UK population estimate of 7,831 pairs (95% confidence limits: 5835-10143).
This compares with the previous survey estimate of 10 000 pairs (95% confidence limits: 6300-14600) in 1999: a decline of 21%. Although this change in population estimates was not statistically significant, the fall in population size reported by the survey is supported by results from Bird Atlas 2007-11, organised by the British Trust for Ornithology, which recorded an 18% decline in the 10-km square breeding range between 1988-91 and 2008-11.
Scotland held 98% of the UK population with an estimate of 7640 pairs; 18% lower than in 1999. In England, however, the population declined by 72% from an estimated 587 pairs in 1999 to just 164 pairs in 2013. The very small populations breeding in Wales and Northern Ireland were estimated at 16 and 18 pairs, respectively.
This latest survey shows that the islands and seaboard of northwest Scotland continue to be strongholds for breeding twite, where they are strongly associated with areas of extensively managed agriculture.
A previous study by the RSPB found that the distribution of moorland nesting twite on the Western Isles was concentrated close to adjacent farmland, where the mix of extensively grazed pastures and cultivated fallows provide a variety of habitats rich in weeds for adults provisioning nestlings with seed food throughout the breeding season.
Moreover, overall breeding productivity in the Western Isles was higher than in a concurrent study of the declining twite population in the English south Pennines due to lower rates of nest loss and a much greater frequency of repeat nesting.
Collectively, this area supports the large majority of the Scottish and UK twite population, highlighting the importance of the high nature value farming systems that characterise agricultural land use here.
Causes of decline
The causes of twite population declines are not fully understood but are likely related to a reduction in seed food supplies in both breeding and wintering areas due to changes in farming practices, loss of pioneer saltmarsh on their English coastal wintering grounds and, at least in England, loss of suitable moorland nesting habitat due to changes in management and land use.
In England, the vast majority of the population was found in the south Pennines. Repeated systematic surveys funded by Natural England (NE) have recorded substantial declines between 1990 and 2014 in what was formerly regarded as a stronghold for twite in England.
Conservation measures to recover the Pennine population have been implemented since 2010, under a project funded by RSPB and NE (through the Action for Birds in England partnership).
These focus on restoring flower-rich meadows and pastures close to twite moorland nesting areas and are being delivered through government funded Higher Level Stewardship agri-environment scheme agreements.
Following monitoring work in 2016 showing a further decline in numbers, we are now undertaking analyses of twite demographic data sets from a number of studies to understand whether low productivity or survival is driving the decline of this population.
Similarly, in Wales, trial conservation management (in this case, rotational grazing of pastures) has been deployed on farmland to increase seed food supplies throughout the breeding season as part of conservation efforts to recover the small population breeding in northern Snowdonia.
Further work is now required to understand the demographic and environmental drivers of population change across breeding populations.
Read the paper for full details of the survey, which was funded by the RSPB, Scottish Natural Heritage, NE and Natural Resources Wales.
Blog post by Prof. Richard Gregory, Head of Species Monitoring and Research, RSPB Centre for Conservation Science.
Biodiversity is in trouble.
The State of Nature report showed us that 56% of species were declining, 40% showing strong to moderate declines, and a relatively high proportion of UK species were threatened with extinction.
Yet we know that well-planned conservation interventions work and our protected areas have played a massive role in helping to restore iconic species, like the large blue butterfly, bittern, lady’s slipper orchid, pool frog and sand lizard, and they could do much more in the future.
Making space for nature
The publication in 2010 of the highly influential Making Space for Nature report led by Professor Sir John Lawton threw down the gauntlet for nature conservation in England but made for depressing reading.
Lawton’s panel was asked to review the state of our wildlife sites and whether they were capable of responding and adapting to the growing challenges of climate change and other demands on our land. The answer was a resounding no.
Our sites were judged too small and too isolated, leading to declines in many of our characteristic species, and with climate change, things were only going to get worse.
This is bad news for wildlife, and bad news for us, because damage to nature means the environment is less able to provide the many ecosystem services upon which we depend. Lawton concluded that we needed more space for nature.
He suggested that rebuild needed to: (1) improve the quality of current sites by better habitat management, (2) increase the size of current wildlife sites, (3) create new sites, (4) enhance connections between, or join up, sites, and (5) reduce the pressures on wildlife by improving the wider environment, including through buffering wildlife sites (Figure 1).
Figure 1. An idealised ecological network. Plausible actions to increase network resilience include improving the condition (A) or size (B) of existing sites, creating new sites (C), creating features that facilitate dispersal (D) and softening the matrix (E).
Lawton’s mantra of Better, Bigger, More and Joined (BBMJ) is a genuine game-changer in nature conservation and its influence can be seen across the sector, and significantly, within the government’s ambitious new 25-year environment plan for England, and yet there has been little progress towards delivering this vision.
What is a resilient ecological network?
In a new paper just published, a group of academics and conservationists, including myself, looked at why this might be the case and how to move forwards practically. We think that a part of the answer, at least, reflects a lack of clarity about what a ‘resilient ecological network’ would look like and how you know if you had one, or not.
We go on to suggest five immediate actions, mirroring Lawton’s recommendations (BBMJ), that would contribute to delivering a resilient ecological network with a low risk of unintended consequences and high probability of positive benefits for wildlife and people (See appendix).
Our recommended actions are similar to those in the 25-year environment plan for England, but go further and are more ambitious.
Planning for nature conservation has increasingly emphasised the concepts of resilience and spatial networks, and although the importance of habitat networks for individual species is clear, their significance for long-term ecological resilience and multi-species conservation strategies is less well established.
Referencing spatial network theory, we describe a way of defining and assessing a network of wildlife areas that supports species’ resilience to multiple forms of perturbations and pressures. Building existing theory into useable and scalable approaches applicable to large numbers of species is challenging, but tractable.
We suggest a simple framework for designing and delivering a resilient network (Figure 2).
Figure 2. Adaptive Management Cycle for implementing a resilient ecological network. Features of the existing network would be evaluated regularly to determine the likelihood that the vision will be achieved (1). Plausible conservation actions focussed on sites or species would be identified (2) and evaluated for their potential to improve network resilience (3). Actual conservation actions are directed at sites or species (4), and their effectiveness monitored (5).
What are the paper's implications?
While the concept of resilient ecological networks has attracted scientific and political support, to date there is no consensus on what a resilient network would look like, or how it would be assessed.
Importantly, it is also unclear whether existing bold targets for action, such as those in the 25-year environment plan for England, would be sufficient to achieve network resilience. We just don’t know.
We show in our paper however that the scientific principles to place resilience and network theory at the heart of large-scale environmental planning are established and ready to implement.
We argue that delivering a resilient network to support nature recovery in England is achievable and can be integrated with ongoing conservation actions and targets by assessing their effectiveness on properties of the entire network as a whole.
England’s 25 Year Environment Plan promises to deliver a natural environment that is protected and enhanced for the future and so provides the ideal testbed to deliver and test the theory. We argue for a more ambitious ecological network that benefits wildlife and people.
See the full paper in the Journal for Applied Ecology
Reference: Isaac NJB, Brotherton PNM, Bullock JM, Gregory RD, Boehning-Gaese K, Connor B, Crick HQP, Freckleton R, Gill J, Hails RS, Hartikainen M, Hester AJ, Millner-Gulland EJ, Oliver T, Pearson RG, Sutherland WJ, Thomas CD, Travis JMJ, Turnbull LA, Willis K, Woodward G & Mace GM. (2018) Defining and delivering resilient ecological networks: nature conservation in England. J. Appl Ecol.
Potential targets for delivering Better, Bigger, More and Joined wildlife sites in England.
(1) Sites of Special Scientific Interest (SSSI), National Nature Reserves, Special Protected Areas, Special Areas of Conservation, and Ramsar sites. Although the levels of protection vary across categories, with the highest afforded to the international designations, all categories are also designated as SSSIs, and it is this designation that provides the reporting framework for all protected areas.
(2) ‘Favourable condition’ indicates that the designated feature(s) within a site are being adequately conserved, appropriately managed, and are meeting site-specific monitoring targets, which are subject to regular review
Blog post by Prof. Jeremy Wilson, Head of Research in Scotland, RSPB Centre for Conservation Science
England’s loss but Scotland’s gain
Once part of the soundtrack of an English summer, the call of the cuckoo is now a fading memory for many. We have lost over three-quarters of the UK cuckoo population since the 1980s yet know little of the reasons why.
Yet more intriguingly, changes in cuckoo numbers vary dramatically across the UK; in England, the Breeding Bird Survey organised by the British Trust for Ornithology (BTO) has documented a 70% decline since 1995, whilst the Scottish population has increased by 30%, a trend apparent especially in the Highlands (Figure 1).
More locally, it is clear that cuckoos are faring much better in areas of heathland, especially in the uplands, than in the farmed lowlands. Nowhere is this more apparent than in Devon, where cuckoos were widespread across the county in the 1980s, but are now confined to the margins of Dartmoor and Exmoor.
Fig. 1. Changes in abundance of Cuckoos between the 1988-91 and 2007-11 Atlases.
A unique challenge
Trying to understand these complicated patterns of change presents a unique challenge. Adult cuckoos are present in the UK for only a short time each year, arriving from April and often gone by July.
And of course they are brood parasites so that the habitat and feeding conditions necessary for cuckoo breeding success must match those of their main hosts – meadow pipits, reed warblers or dunnocks – whose usurped nesting attempts raise cuckoo nestlings to fledging.
On top of all that, for the brief period that cuckoos are with us, they specialise in feeding on large, hairy moth caterpillars such as the ‘woolly bears’ of the garden tiger (Fig. 2), that are toxic to most other birds.
Fig. 2. A ‘woolly bear’ - the caterpillar of the garden tiger moth and a key prey item for adult cuckoos. Photo credit: © Jeremy Wilson.
Exploring the patterns
The stark patterns in the fortunes of Cuckoos became the focus of a PhD study undertaken by Chloe Denerley and supported by the University of Aberdeen, the RSPB and Natural England.
Chloe worked at two scales – both in the field in a study area in Devon, but also using national data sets describing populations of cckoos and their hosts (the BTO/JNCC/RSPB Breeding Bird Survey), habitats (the Centre for Ecology & Hydrology’s Land Cover Maps) and population changes of moths (Rothamsted Research’s light trap network).
At both scales, Chloe analysed the breeding distribution of cuckoos in relation to habitat variation, the abundance of hosts and the abundance of moths whose caterpillars are a key food of adult cuckoos.
A female Cuckoo on Dartmoor. Photo credit: © Professor Charles Tyler, University of Exeter
In Devon, cuckoos were found more often in areas with more semi-natural habitat and more meadow pipits (but fewer dunnocks) and where, later in the summer, higher numbers of moths were light-trapped whose larvae are cuckoo prey.
Nationally, cuckoos have become more associated with upland heath with meadow pipits, and with wetland habitats with reed warblers, and the distribution of cuckoos has shifted from south to north within the UK.
The abundance of moth species preyed upon by cuckoos has declined four times faster than that of other moths. The abundance of these moths has shown the sharpest declines in grassland, arable and woodland habitats and has increased in semi-natural habitats (heaths and rough grassland).
The conservation implications
Overall, Chloe’s findings suggest that agricultural change in the UK may well have played a part in driving cuckoo declines, pushing the birds increasingly out of the farmed countryside and into heathlands and the uplands.
The ideal next step to test the feasibility of restoring Cuckoo populations more widely would be a replicated, landscape-scale intervention.
This should focus on the coordinated restoration of species-rich grassland, reduced pesticide use on arable land, hedgerows with less-than-annual trimming and minimal understorey disturbance, and grass field margins not subject to agrochemical application, ideally located close to a remaining centre of cuckoo population such as Dartmoor.
Equally, Cuckoos might be expected to respond well to existing large-scale ecological restoration projects across a wide variety of landscapes from wetlands, to rewilding interventions in agricultural landscapes, to the uplands. Coordinated monitoring of moth, host and Cuckoo numbers across such projects could tell us much about the long-term prospects for reversing Cuckoo population losses in the UK.
Read the paper at https://onlinelibrary.wiley.com/doi/full/10.1111/ibi.12612
Denerley, C., Redpath, S.M., van der Wal, R., Newson, S.E., Chapman, J.W. & Wilson, J.D. (2018) Breeding ground correlates of the distribution and decline of the Common Cuckoo Cuculus canorus at two spatial scales.