Ring ouzel

Overall vulnerability

Feature assessed:

• Ring ouzel (Turdus torquatus)

Special qualities:

• Internationally important and locally distinctive wildlife and habitats

Feature description:

The ring ouzel is a distinctive thrush species found in the PDNP uplands. Despite looking quite similar to the more common blackbird, it is easily distinguishable by its white bib. A summer migrant, ring ouzel spends winter in North Africa before returning to the PDNP to breed. Often nesting in the rocks and cracks of gritstone landforms, ring ouzel are found in the Dark and South West Peak and have a stronghold in the Eastern Moors area. Their diet is similar to that of other thrushes, consisting of earthworms, beetles, and other ground invertebrates as well as berries. As such, adjacent areas with feeding resource including unimproved grassland, scrub, and verges are essential to good ring ouzel habitat. The ring ouzel is a rare upland species in the UK, with the PDNP holding a significant proportion of the UK population.

How vulnerable are ring ouzel?

Ring ouzel 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 declining current condition, and a low adaptive capacity.

Ring ouzel population trends in the PDNP appear to be following the national trend, declining and retracting to upland locations. Changing conditions and mismatch in the timing of food availability may mean that in the future, suitable habitat can only be found north of the PDNP. Greater disturbance from increased visitor numbers may also have a significant effect. Despite their reasonable dispersal ability, ring ouzel are unlikely to adapt quickly enough to match changing conditions, and management interventions are not well known enough to counter this.

Current condition:

The ring ouzel has undergone significant historic decline across the UK, with numbers continuing to drop in recent years. This trend appears to be true for PDNP ring ouzels, with the 2004 Moorland Breeding Bird Survey showing a decline in abundance and territory. Ring ouzel distribution appears to have contracted to upland moorland sites with good heather cover, away from conifer plantations. There is much of this habitat type in the PDNP, which may imply the PDNP is more suitable than other areas, although there is no evidence to explain different rates of decline across the country. Conifer plantations are currently being reduced in area in the PDNP, giving possible opportunity for population expansion. Predation of nestlings and fledglings may be a limiting factor in ring ouzel populations, but it is unclear to what degree.

Ring ouzel are very sensitive to disturbance. This is a significant factor in the heavily visited PDNP. As many nest in gritstone crags, disturbance from climbers and scramblers is an ongoing issue. Ring ouzel are thought to have been lost from the Roaches due to disturbance from climbers. Recent efforts to limit access to crags during nesting season have been successful in reducing disturbance around the Stanage Edge area. Factors outside the PDNP are also important, with some birds being lost to illegal hunting along their migration route, and habitat loss due to juniper forest damage in their wintering grounds.

What are the potential impacts of climate change?

Overall potential impact rating

Direct impacts of climate change

Warmer summers may have negative effects on ring ouzel populations. Rising temperatures have been correlated with range contractions from low altitudes in European ring ouzel, and could already be affecting PDNP populations. This would reduce the amount of suitable habitat in the PDNP, restricting them to higher crags and moorland only. This could be particularly devastating if the Eastern Moors become unsuitable, as they currently contain the largest ring ouzel population in the PDNP. Phenological mismatch has been suggested as the cause of poor ring ouzel performance following warmer summers elsewhere in Europe. A correlation between warm summers and a decline in territory the following year has been found to exist irrespective of summer rainfall. While the cause is unclear, it may be related to a mismatch in earthworm availability. This effect could extend to the PDNP population as temperatures rise. Data Certainty: High An increase in spring and summer drought could increase this effect by reducing invertebrate prey availability. Soil and ground invertebrates, especially earthworms, are sensitive to dry ground conditions, reducing in abundance and moving deeper into the soil column. This reduction in food resource during the breeding season would result in decreased breeding success in ring ouzel. Data Certainty: Moderate

Human behaviour change

Hotter drier summers are likely to increase visitor numbers to the PDNP, also increasing the risk of disturbance to breeding ring ouzel. PDNP ring ouzels are known to have significantly better nesting success when disturbance is at a minimum. Therefore, rising numbers of rock climbers and other visitors could decrease nesting success significantly. Data Certainty: High

Changes in conditions in the PDNP will prompt changes in human land use. While this effect in unpredictable, any increase in management intensity may have negative effects on ring ouzel populations. Birds nesting in heather may be particularly at risk from overstocking or increased burning. Data Certainty: Moderate Higher grazing pressure on heather moorland would increase nutrient loading and erosion, changing the character of the heathland. These changes to the habitat mosaic may result in reduced occupancy and breeding success in ring ouzel. Data Certainty: High An increase in climate change mitigation may disadvantage PDNP ring ouzel populations via habitat loss. Afforestation is a popular carbon capture method but can remove ring ouzel habitat by replacing the upland heather stands preferred for ground nests. Afforestation is likely to be more popular in steep gullies due to natural flood management benefits, these gullies being good ring ouzel habitat. Data Certainty: Moderate

Other indirect climate change impacts

While drier summers may not be the most significant factor affecting breeding success, reduced availability of ripe fruit and berries during late summer and autumn would reduce pre-migration condition in ring ouzel. Changes to rainfall in North African wintering grounds may also affect ring ouzel populations. Reduced occupancy in ring ouzel has been shown to occur 24 months after wet springs in Morocco, probably due to effects on juniper flowering. Therefore, changes in rainfall may increase ring ouzel migration fatalities and result in poorer post-migration condition. Data Certainty: High

In the PDNP, wetter winters and flooding may increase waterlogging of soils, disadvantaging sensitive species such as heather in affected areas. This would not only reduce suitable nesting habitat but could also create bare ground for invasive plant species to move in and dominate. Data Certainty: High

Increased atmospheric carbon dioxide concentrations and higher temperatures may cause increased plant growth and biomass on heathlands. Combined with dry ground conditions and drought, this may lead to an increased incidence of wildfire, especially on dry heather moorland. Wildfire leads to habitat loss and may destroy nests for those ring ouzels not nesting in rock crevices. Wildfire also has negative effects on earthworm and other ground invertebrate populations. Data Certainty: Low

Invasive or other species interactions

Warmer wetter conditions in winter may lead to increased prevalence of diseases and pest species. Bilberry are susceptible to Phytophthora, incidence of which may increase as conditions become more suitable for its spread. Bilberries are a vital autumn food resource, so reduced extent and fruiting would have a significant impact. A reduction in food availability during the weeks leading to migration would result in greater migration fatality. Data Certainty: Moderate

Increased annual average temperatures may lead to increased winter survival of small mammals such as weasels and stoats. This may cause decreased survival of ring ouzel nestlings and fledglings. However, warmer winters may also increase populations of preferred prey such as rabbits, reducing predation pressure on ring ouzel. Data Certainty: Low

Higher concentrations of carbon dioxide and other greenhouse gases may lead to an increase in plant growth rate, decreasing ring ouzel nesting success. A taller sward height could reduce access to invertebrates for foraging, and scrub encroachment would result in less preferable nesting habitat. However, some encroachment of scrub may be beneficial for ring ouzel as part of a habitat mosaic, providing berries in late summer and higher soil invertebrate abundance. Data Certainty: Low

Sedimentation or erosion

An increase in winter rainfall and summer storm events would result in increased runoff and soil erosion on heathland. Soil and peat on much heather moorland in the PDNP is already relatively thin, meaning that soil erosion can cause significant root damage to heather. Some nesting habitat may therefore be lost, and the habitat mosaic altered. Data Certainty: High

What is the adaptive capacity of ring ouzel?

Overall adaptive capacity rating

Ring ouzel have significant barriers to adaptation to future climate change. Ring ouzel in the PDNP are at the south-eastern limit of their UK breeding range, meaning that any northward shift in their climate space is likely to cause their loss from the PDNP. Modelled shifts in habitat suitability show this loss to occur by the late 21st century. Ring ouzel in southern Europe have different habitat requirements and habits, but these are separate sub-species and there is no evidence of gene flow with UK populations. Data Certainty: High

However, ring ouzel do have some capacity for population recovery. As migratory birds, their dispersal ability is potentially good, although they are faithful to nesting sites. Ring ouzel are long lived, allowing some scope for recovery from low breeding success if conditions improve. However, this also means ring ouzel are unlikely to have high evolutionary capacity or behavioural adaptation. European sub-species could in theory assist with recovery and adaptation, but this seems unlikely, as there is little evidence of genetic admixture. Data Certainty: Low

More information is needed to manage for ring ouzel effectively. Many of the causes of decline are not well understood, and probably relate to factors such as migration routes and wintering grounds. Reducing human disturbance at breeding sites appears to help, but this alone is unlikely to offset climate effects. Data Certainty: Moderate

Some financial resources may be available to build resilience of the ring ouzel in the form of environmental land management schemes. However, these are limited and in many cases there are barriers to implementation. It is also impossible to predict how these will change over the coming years, and they are especially uncertain at present. Data Certainty: Low

Institutional support would assist ring ouzel adaptation. Many of the current ring ouzel population centres are managed by conservation organisations, such as the Eastern Moors and Dove Stone Partnerships. However, the Eastern Moors population is on the edge of ring ouzel range latitudinally and altitudinally, so the value of this stronghold may decrease in the future. Ring ouzel are also a red listed bird species in the UK, a status that may increase the chances of adaptation management occurring. Data Certainty: Moderate

Key adaptation recommendations for ring ouzel:

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.

• Non-native upland forestry plantations remove good ring ouzel habitat and should be phased out where they are impacting ring ouzel populations.
• Predator control could be a useful tool in high predator density areas, but may inadvertently increase predator populations and disrupt other species interactions. 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.

• Manage visitor access and disturbance during sensitive breeding season will increase ring ouzel breeding success, and thus help reduce non-climate related pressures.

Improve current condition to increase resilience: Increase structural diversity to improve resilience at a landscape scale

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations focus on increasing the structural diversity of the area or habitat in which the feature is found. This can help to offset the effects of climate change on the feature, as well as to allow it to be in a better position to recover from future climate changes.

• Move towards a habitat mosaic for ring ouzel. This includes open areas and heterogeneous vegetation structure, with some scrub in appropriate areas.
• Appropriate cutting or grazing to create varied vegetation structure would be beneficial to ring ouzel and reduce wildfire risk.