Short-eared owl

Overall vulnerability

Feature assessed:

• Short-eared owl (Asio flammeus)

Special qualities:

• Internationally important and locally distinctive wildlife and habitats

Feature description:

The short-eared owl is a charismatic moorland bird of prey, breeding in the PDNP each year before migrating to lowland and coastal wintering grounds. One of the most widespread owl species in the world, the short-eared owl breeds from South America to Russia. However, the PDNP represents the southern edge of their UK breeding range. One of the most active UK owls in daylight, short-eared owl can easily be seen on their hunts for voles and other small mammals due to their relatively large size and pale brown body. Within the PDNP, moorland in the Dark and South West Peak is preferred habitat, where they nest in scrapes on the ground. Short-eared owl are a conservation priority in the UK and Europe. As a bird of prey, they are a good indicator of ecosystems with robust prey populations.

How vulnerable are short-eared owls?

Short-eared owl in the PDNP have been rated ‘high’ on our vulnerability scale. This score is due to high sensitivity and exposure to climate change variables, with a poor but recovering current condition, and a moderate adaptive capacity.

Short-eared owl populations in the PDNP appear to be recovering from historical decline despite continuing threats. Climate change effects on their small mammal prey may have a significant impact on short-eared owls. They are a widespread and mobile migrant, so short-eared owls are quite adaptable to changing conditions. However, this may include moving out of the PDNP. Conservation actions taken in the PDNP could assist short-eared owls in adapting to changing conditions.

Current condition:

Short-eared owl are in long-term decline across the UK, with an almost 50% contraction in range in the past 50 years. This trend appears to have been reversed in the PDNP in recent years, with the 2004 Moorland for the Future Breeding Bird Survey showing an increase in short-eared owl abundance and territory. 15 or more pairs were estimated to be nesting in the PDNP in 2018. Short-eared owls do not appear to be overly disadvantaged by other species interactions. Foxes, or more likely dogs, may disturb and occasionally injure a bird, especially during nesting season. Other birds of prey such as harriers and other owl species may compete with short-eared owls for prey resources but the impact of this is probably minimal.

Human land use is the most important limiting factor for short-eared owl numbers. Sheep grazing has been shown to negatively affect vole abundance, with both vole numbers approximately doubling under reduced grazing. Purple moor-grass grassland is good vole habitat, but is uneconomic and of low conservation value, so is being lost to other habitat types. Illegal persecution of short-eared owls does occur, and because they are active in daylight, they are easy to spot and kill. As an apex predator only a few need to be killed to have a large impact on populations. Wildfire is also an issue, affecting both heather and purple moor-grass moorland, removing habitat and destroying nests.

What are the potential impacts of climate change?

Overall potential impact rating

Direct impacts of climate change

Increased annual average temperatures may be beneficial to short-eared owls in the PDNP in the short term, but could result in their loss in the longer term. Milder winters may mean greater survival at their wintering grounds, as well as shorter migration distances due to closer suitable conditions. Better owl condition after return from migration could also increase breeding success. However, these benefits may eventually be lost, as suitable climate space is predicted to shift northwards. Short-eared owl in the PDNP are at the southern edge of their UK range in the PDNP and modelling suggests this may result in their loss. Data Certainty: Moderate

Increased winter rainfall may be detrimental to short-eared owl populations. European owl breeding success is known to be sensitive to wet winters, with higher breeding probability and larger clutch size resulting from colder and drier winters. As winters are predicted to become wetter and warmer, this may reduce short-eared owl breeding success and reduce population replenishment. Data Certainty: Low An increase in the frequency and intensity of storm events could compound this effect, as ground nesting birds are often sensitive to heavy rainfall during nesting. Data Certainty: Low

Increased concentrations of atmospheric carbon dioxide coupled with increased temperatures may lead to an increased plant growth rate in some areas. This could be beneficial to short-eared owl populations by increasing habitat suitability. Vole populations may increase as rank vegetation increases and grassland expands, and short-eared owls will have a greater access to nesting materials. Data Certainty: Low

Human behaviour change

Changes in human behaviour and land use have the potential to negatively affect short-eared owl in the PDNP. As the climate changes, suitability of some parts of the PDNP for different management types will change, leading to an unpredictable human response. If agricultural ‘improvement’ of moorland fringe grassland becomes more viable, this could result in feeding habitat loss and therefore displacement or population decline. Changes to grouse moor management may also be important; if grouse populations decline as a result of environmental change, an increase in management intensity may result. Data Certainty: Moderate

Construction of coastal flood defences and hard barriers may reduce short-eared owl populations by degradation and removal of their coastal wintering habitats, except where these create large areas of new habitat. As seas levels rise, management interventions such as these may become more common. Hard barriers will prevent habitat moving with sea level rise, resulting in squeezing of current habitat. Some wintering locations may therefore be lost to the sea, and saltification may affect some of the remaining habitats. This would increase competition and reduce the suitability of coastal wintering grounds, reducing short-eared owl wintering survival and condition upon return from migration. Data Certainty: Low

Other indirect climate change impacts

Short-eared owl populations fluctuate with the populations of their vole prey. As climate change places additional stressors on voles, these fluctuations may become more pronounced. Rainfall and soil moisture changes have a significant effect on voles, and extreme events can severely reduce juvenile survival. The increased variability in annual conditions may therefore cause both vole and short-eared owl populations to become more variable. Data Certainty: Moderate

Hotter, drier conditions during the summer months may effect an increase in wildfire in the PDNP. The resulting habitat loss and nest destruction would cause decreased breeding success in short-eared owl. Purple moor-grass moorland is very susceptible to wildfire blazes during drought, meaning that good short-eared owl habitat is some of the most at risk from this damage. Data Certainty: Low

Invasive or other species interactions

Warmer winters may increase survival of generalist predators such as red fox. Increased annual average temperatures may lead to a greater prevalence of short-eared owl diseases and pests. This would result in reduced survival of short-eared owls. Data Certainty: Low This could also affect their vole prey. As vole numbers fluctuate cyclically, disease outbreaks or extreme weather could compound the population lows, causing poor vole years to decrease short-eared owl fitness even further. Data Certainty: Low

Sedimentation or erosion

Sea level rise may cause increased erosion on short-eared owl wintering grounds, reducing wintering survival. Erosive forces may change coastal habitats by removing and redepositing sediment, and changing substrate structure. This change in substrate structure may reduce invertebrate abundance and vegetation communities and therefore the abundance or availability of prey. Habitat loss and reduction in prey populations combined could affect short-eared owls over winter, lowering survival rates and resulting in poorer condition upon return from migration. Data Certainty: Low

What is the adaptive capacity of short-eared owls?

Overall adaptive capacity rating

Short-eared owl in the PDNP have low overall capacity for recovery from loss. The population is relatively small, with a low breeding success, meaning population growth is slow. However, short-eared owl have a large population across Europe, which could bolster a declining population. Winter migrants are present in many places further south, so there are likely to be some short-eared owl in the PDNP during winter even if the breeding population is lost. Data Certainty: Low The short-eared owl’s status as a small mammal specialist on moorland may also provide some barrier to recovery, as they are heavily dependent on a specific set of food resources. Data Certainty: Very High

As a widespread migratory bird, short-eared owl have few barriers to movement. They are nomadic, and move within the UK and between the UK and Europe. In the PDNP population, the number of migrating birds and their destinations are unknown, but it is likely that migrants can provide some input to the population. The high dispersal ability of short-eared owl means that they are likely to be able to move as a response to climate change. This could result in the South West Peak population moving to the Dark Peak, or short-eared owls moving out of the PDNP entirely. Data Certainty: Moderate

Some funding is available to assist short-eared owl adaptation, at least indirectly. Moorland restoration projects which may benefit short-eared owls by reducing the impacts of climate change on their habitat, already exist in the PDNP. Data Certainty: Moderate

Institutional and organisational support can help support short-eared owl populations in the PDNP. The Peak District Birds of Prey Initiative was designed to involve partners in increasing bird of prey populations and reducing illegal persecution, targeting several species including short-eared owl. However, the project has generally failed to meet its own targets, and its future looks uncertain. Other projects such as the RSPB’s Upland Skies partnership may able to provide a complementary role through public and landowner engagement. The South Pennine Moors Special Protection Area (SPA) is designated for bird species including short-eared owl, and so provides some level of protection. Short-eared owl are an amber listed bird species in the UK and are protected under the Wildlife and Countryside Act 1981. Data Certainty: Moderate

Management options are available in the PDNP for short-eared owl, mostly though sensitive management of the moorland habitats they depend on. However, detailed information on the migration habits, nesting areas, and breeding success of these birds are unknown, meaning it is difficult to identify and respond to changes in short-eared owl populations. Data Certainty: Moderate

Key adaptation recommendations for short-eared owls:

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.

• A greater focus on bird of prey persecution is needed.
• Lower sheep grazing densities in short-eared owl habitat could benefit owl populations by increasing the populations of their small mammal prey.
• Study into migration habits of short-eared owl could clarify the resident status of PDNP birds, informing management.
• Partnership approach with coastal wintering grounds would be beneficial to short-eared owl conservation.
• 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.

• Monitoring of known breeding pairs could increase the information resource available.
• 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.