Dunlin

Overall vulnerability

Feature assessed:

• Dunlin (Calidris alpina)

Special qualities:

• Internationally important and locally distinctive wildlife and habitats

Feature description:

The dunlin is a small wading bird, which is a rare breeder on moorland in the Dark Peak. They are much smaller than a snipe or curlew, but still have the distinctive long bill of a wader. Dunlin nest in scrapes on moorland during the spring and summer, leaving for the coast in the autumn where they gather in large flocks. While in the PDNP dunlin are in their breeding plumage: a rusty-brown back with white underparts, and a black patch on the belly. They mainly feed on soil invertebrates by probing soft ground, and prefer wet ground for this reason.

How vulnerable are dunlin?

Dunlin in the PDNP have been rated ‘very high’ on our vulnerability scale. This score is due to high sensitivity and exposure to climate change variables, with a moderately unfavourable current condition and a low adaptive capacity.

Dunlin populations in the PDNP have been in decline historically, but recent increases in some areas are a positive sign for the population as a whole. Dunlin are a relatively mobile species, and rising temperatures are likely to cause breeding populations to move northwards and be lost from the PDNP. Further loss of blanket bog functionality may also disadvantage dunlin populations due to reductions in their invertebrate prey. Blanket bog restoration has proven very beneficial for dunlin, but is may not be enough to retain breeding populations in the future.

Current condition:

Dunlin appear to have a small but relatively stable breeding population in the Dark Peak. The 2004 Moorland Breeding Bird Survey showed a decline in breeding dunlin, but local data now shows increases in some areas. Moorland rewetting efforts appear to have assisted recovery and population expansion is possible when degraded habitat is restored. The PDNP dunlin population is at the southern edge of its modelled breeding range in England. However, it is worth noting that a small breeding population on Dartmoor persists much further south and outside of this modelled range.

Upland moorland in the PDNP is still heavily polluted as a legacy of the industrial revolution. Heavy metals are present and pH levels are very low. This will reduce soil invertebrate activity and abundance, reducing food resources for dunlin and other waders.

Extensive erosion of peatlands in the PDNP has severely reduced habitat suitability for dunlin. Drainage and exposure of peat has led to gullying and drying out of soils, reducing invertebrate populations such as cranefly larvae. Moorland rewetting efforts have gone some way to counter this in recent years, but much work remains to be done.

Wildfire has likely removed large areas of dunlin habitat periodically, slowing population recovery. In the degraded and well-visited uplands of the PDNP wildfire is common. Fire may have destroyed nests and prevented re-nesting by clearing large areas.

Visitor disturbance will have some impact, but this effect is likely to be restricted to the most popular sites and near footpaths. High visitor pressure has been shown to affect upland waders in the most heavily visited areas, but some studies have shown no significant effects on breeding bird populations in the PDNP. Dunlin nesting at popular sites such as Dove Stone will be more at risk from disturbance.

As ground nesting birds, dunlin are likely impacted by generalist predators such as red fox and carrion crow which will take young birds at the nest, and possibly even adult birds due to their small size.

What are the potential impacts of climate change?

Overall potential impact rating

Direct impacts of climate change

Increased average annual temperatures may have mixed effects on dunlin populations. The number of reported dunlin fatalities have been found to increase during severe winters, so warmer winters may lead to greater dunlin survival at their wintering grounds. However, rising temperatures may move suitable habitat space northwards over the next century. Dark Peak dunlin are on the southern edge of the Pennine breeding population, so local populations will be some of the first to feel this effect. Models show that even under mild warming scenarios, breeding dunlin will likely be lost from most of England, becoming restricted to the Scottish highlands. Therefore, any population gains from warming winters may not affect the PDNP as dunlin move north out of the area and are lost. Data Certainty: Very High

Drier summers and increased drought frequency may cause changes in dunlin habitat. Much of the degraded bog in the PDNP is already functionally dry heath, with drought tolerant species such as heather dominating. Drier conditions may exacerbate this change and make rewetting efforts more difficult. If habitats become drier, soil invertebrate populations will decline and foraging will become more difficult in harder ground. Dunlin breeding success would therefore decline as food resource availability decreases. Data Certainty: High Greater weather extremes may contribute to habitat damage and degradation. Cracking and shrinkage of peat during more frequent drought is likely to make degraded peatlands more susceptible to erosion. Erosion will be greatest during storm events, increasing gully size and forming new gullies and peat pipes. As a result, damage to dunlin nesting and feeding habitat is likely to increase, reducing dunlin breeding success. Data Certainty: High

Human behaviour change

As weather conditions become more variable, intensification of land management may be used to counter these effects. While it is impossible to predict the human response to climate change, any intensification of grazing pressure or rotational burning regimes would negatively affect dunlin populations. High stocking levels would increase disturbance and decrease habitat suitability, and burning management can remove habitat. Dunlin breeding on agricultural land and grouse moors could therefore have reduced breeding success as the remaining wet areas are lost. Data Certainty: High

Sea level rise may cause an increase in construction of coastal flood defences and coastal realignment in dunlin wintering grounds. This could remove or squeeze the coastal habitat available to dunlin, and increase competition for resources. However, some coastal realignment may increase the size of mudflats opening up new opportunities for winter sites. Winter survival rates may be reduced overall, along with poorer body condition upon return to the PDNP. Dunlin breeding success may decrease as a result. Data Certainty: High

Hotter drier summer conditions may cause a rise in visitor numbers in the PDNP. More traffic on footpaths, a greater numbers of dogs and walkers crossing open moorland would increase disturbance to nesting birds. The result of such disturbance is unclear, but it is a reasonable assumption that it would negatively affect populations to some degree. Data Certainty: Moderate

As climate change advances, carbon capture efforts are likely to increase. In the PDNP, bog restoration and rewetting will probably form a large part of this effort, improving and increasing dunlin habitat. As habitats become wetter, prey abundance and accessibility and therefore dunlin breeding success will increase. Data Certainty: Moderate Bog restoration as a natural flood management method may increase to counter more frequent and severe flooding. Dunlin habitat suitability and therefore breeding success would therefore increase, at least temporarily until the lack of rainfall or drying outweighs the benefits of the rewetting. Data Certainty: Low

Other indirect climate change impacts

Increased annual average temperatures may have negative effects on dunlin populations through interactions with their invertebrate prey. Invertebrate productivity increases with temperature to a point, but begins to decline as temperatures rise further and soils dry out. Although dunlin may benefit from temperature rises at first, they could later decline as their prey becomes less available. Several drought years in a row could negatively affect breeding bird fledging success if invertebrate numbers become very low. Data Certainty: High

Higher temperatures and drier ground conditions may make wildfire more frequent and severe in the PDNP. This could result from accidental ignition or from managed burns running out of control. Degraded bog habitats that are currently dry heather dominated moorland are particularly at risk. Further increases in wildfire would mean more nests lost and less nesting habitat available, reducing dunlin breeding success. Data Certainty: High

Nutrient changes or environmental contamination

Greater winter rainfall and frequency of summer storm events may increase episodic nitrogen deposition. This could disadvantage Sphagnum mosses, especially in combination with summer droughts. Sphagnum mosses would be disadvantaged directly through inhibition of their growth and indirectly by removing their competitive advantage over vascular plants. Sphagnum mosses being lost from bog habitat would result in reduced peat accumulation and drying out of peat. Dunlin prey would be less abundant and accessible, leading to reduced dunlin fitness and breeding success. Data Certainty: High

Changes in annual precipitation cycles could change the nutrient availability in bog ecosystems. A greater hydrological input in winter may cause flushing of the system, preventing already scarce nutrient inputs from entering the system. Conversely, reduced input in summer may increase nutrient availability in some areas through concentration. Such changes in nutrient cycling may negatively affect the bog ecosystem, potentially reducing populations of invertebrate prey. Dunlin would have reduced foraging success and therefore breeding success. Data Certainty: Low

Sedimentation or erosion

Drier summer conditions could increase erosion of degraded peatlands through drying of peat. As winter rainfall and summer storm events are likely to intensify, erosion of peat by surface water would also increase. Greater gullying could occur, further draining the surrounding area. This process could accelerate or restart degradation in moorland undergoing restoration, reducing its suitability as dunlin habitat. Dunlin habitat area and breeding success would therefore be reduced. Data Certainty: High

Invasive or other species interactions

Multiple climate change related effects may act to change the vegetation community of dunlin habitat. Changes in nutrient availability may lead to a greater plant growth rate in some areas. Nitrogen deposition events could increase due to greater winter rainfall and summer storm frequency, causing faster growth rates in some species.

Increased average temperatures could also contribute by lengthening the growing season, increasing sward height and scrub growth rate. Invasive plant species may colonise larger areas. Dunlin nest sites require good visibility over the surrounding area, meaning there may be reduced nesting opportunities for dunlin. Data Certainty: Moderate

What is the adaptive capacity of dunlin?

Overall adaptive capacity rating

Dunlin are a mobile species with few barriers to population spread and movement. However, there is no population to the south or east to replace the PDNP population as suitable climate space moves northwards and westwards. Dunlin are likely to react to rising temperatures by moving northwards beyond the PDNP boundary, meaning their loss from the area. Data Certainty: High

Some funding may be available for dunlin conservation in the form of environmental land management schemes. Such schemes would be beneficial through improvement of habitat rather than specific interventions for dunlin conservation. The UK’s exit from the European Union presents opportunities to reform agricultural subsidies to benefit nature, but the future is very uncertain. Data Certainty: Low

Dunlin are protected to some degree by designation. The South Pennines Special Protection Area (SPA) is designated for birds including the dunlin, and much of dunlin territory lies inside the Dark Peak Site of Special Scientific Interest (SSSI). Dunlin are an amber listed bird in the UK and so are of some conservation importance. Organisations working within the PDNP are working towards dunlin population recovery, with the RSPB and United Utilities Dove Stone Estate being a flagship for dunlin conservation within the PDNP. Data Certainty: Moderate

Some knowledge of management interventions for dunlin exists within the PDNP, mostly being focused on moorland revegetation and rewetting. Studies at Dove Stone have shown this to be an effective technique for increasing populations of dunlin and other waders. Management techniques outside of habitat creation and improvement are less well known. Data Certainty: High The dunlin as a species does not appear to have a large capacity to adapt. UK dunlin are reliant on wet bogs with pool complexes for breeding habitat, and suitable coastal habitat for wintering. The Dartmoor dunlin population indicates that dunlin may be able to live outside of what is assumed suitable climatic space, but otherwise dunlin show little evidence of behavioural plasticity. Data Certainty: Low

Key adaptation recommendations for dunlin:

Improve current condition to increase resilience

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations are aimed at improving the condition of the feature at present, therefore making it better able to withstand future changes to climate.

• Rewetting of moorland and blanket bog restoration is the most beneficial intervention for dunlin. Implementation of this management will benefit other waders and have associated benefits of carbon storage and water storage.
• Moorland gully and grip blocking for creation of bog pools creates good feeding habitat for dunlin.
• Upland conifer plantations remove dunlin habitat and should be phased out from areas where they are thought to be limiting populations.
• Partnership with coastal conservation organisations will be the best way to create an integrated management plan, as dunlin may winter in other areas.
• Reducing the number of sheep and therefore lambs may also reduce pressure from generalist predators. Predator control could be a useful tool in high predator density areas, but may inadvertently increase predator populations and disrupt other species interactions. The increase in Dunlin at RSPB Dove Stone has not included predator control, so good quality habitat can counterbalance the effects of predation. Research is needed to determine if a more natural system would be a better option for the future.
• Encourage further uptake of environmental land management schemes by farmers within the PDNP.

Improve current condition to increase resilience: Targeted conservation efforts for important sites and at risk areas

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations are conservation measures aimed at those sites that will have the biggest impact for this feature – either because they are particularly important for the feature or because they are most at risk from climate change.

• Ensure dunlin habitat has well marked and maintained footpaths to prevent encroachment of visitors onto breeding areas.
• Develop fire contingency plans, and ensure management of habitats reduces fire risk e.g. rewetting and increasing species or structural diversity. Influence visitor and behaviour management plans and practices to minimise ignition risk.