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Increased emissions and downfall of nitrogen can alter soil fertility, altering the competitive relationship between plant species, leading to scrub and tree establishment and a subsequent degradation of habitat quality. This process has been proposed as a major factor for declining populations in southern and central Sweden (de Jong & Berg 2001). In a study in western Finland, Valkama and Currie (1998) found higher heavy metal concentrations within Eurasian Curlew eggs in polluted areas compared to control areas. Accumulated PCB residues have been found in adults (Denker & Buthe 1995) and clutches (Boschert 1992, 2004), including some showing very high levels. Generally little is known about the susceptibility of the species to PCBs, but they are not considered a major threat in most countries. All subspecies: whilst pollutants are present within breeding habitats and have been detected within birds, there is no evidence to support whether pollutants have any impact on any demographic parameters (survival rates, hatching success, etc) although there is general consensus amongst experts that it is likely to be having some impact. It has therefore been assessed as ‘unknown’ with the acknowledgment that further research is required (see Section 4. Framework for Action).
New woodland planting can cause both loss and fragmentation of breeding habitat as well as a reduction in the quality of habitat surrounding the new woodland (Douglas et al. 2014). This secondary impact is sometimes referred to as the ‘edge effect’, whereby waders avoid nesting close to forest edges as a possible adaptation to forest edge habitats typically containing higher densities of avian and mammalian predators (Stroud et al. 1990, Valkama et al. 1998, Berg 1992a). Eurasian Curlew have been found to nest further from forest edges than random nest sites (Berg 1992a, Valkama et al. 1998). Predation rates are often higher in landscapes fragmented by woodland (Valkama et al. 1999), the result of which is often reduced productivity leading to population decline. N. a. arquata: Afforestation of breeding habitats is particularly apparent in the UK, where low-grade agricultural land in the uplands is increasingly being converted to forestry; Scotland, which is estimated to host around 55% (~37,400 breeding pairs) of the UK’s Curlew population (O’Brien 2004), has a policy to increase the area of woodland cover from 17% to 25% by 2050 (Scottish Government 2015). Such farmland is often found within landscapes that hold breeding curlew. A recent correlative study suggests that increasing woodland cover from 0-10% within 1km of Curlew breeding sites requires a 50% increase in human predator control effort to achieve population stability (Douglas et al. 2014). This study also found that the negative impact of afforestation was greatest in areas containing high breeding densities. Another study estimated that since the 1950s, 5000 breeding pairs had been lost from a local authority region of Scotland due to the planting of conifer plantations on open ground (Ratcliffe 2007). The issue of inappropriately-sited woodland appears to mostly be confined to the UK. However, since the UK supports approximately 26% of the population (Figure 1) afforestation on breeding grounds has been assessed as ‘medium’. N. a. orientalis: commercial forestry is thought to be increasing across the breeding range (Brown et al. 2014). It has therefore been assessed as ‘low’. N. a. suschkini: commercial forestry is thought to be increasing across the breeding range (Brown et al. 2014). It has therefore been assessed as ‘low’.
Nest and chick predation rates are typically higher in fragmented landscapes (see Section 1.8.4. for details). Inappropriately sited buildings can contribute to habitat fragmentation both visually and by increasing predator densities: building and associated gardens can provide predator perches and nest sites; cats and dogs are frequently introduced to the landscape; and refuse may provide an additional food source to support predators. N. a. arquata: It is unlikely that this threat will occur over a large enough area of the breeding range to have any population-level impact. It has therefore been assessed as ‘local’. N. a. orientalis: Whilst no quantitative data exists, this threat is considered by experts to be increasing across the breeding range and to be having a population-level impact (Brown et al. 2014). It has therefore been assessed as ‘local-medium’. N. a. suschkini: this threat was not perceived by experts to be a threat during a recent review (Brown et al. 2014). It has therefore been assessed as ‘low’.
Oil and gas drilling, with associated roads and service corridors, lead to habitat loss and fragmentation and are important contributors to increasing levels of the human disturbance and pollution issues discussed earlier. N. a. arquata: this threat is very localised and is not thought to be impacting on the population. N. a. orientalis: activities relating to oil and gas drilling are increasing across the breeding range, and whilst no quantitative data exists, this threat is considered by experts to be having some level of population-level impact (Brown et al. 2014). It has therefore been assessed as ‘local-medium’. N. a. suschkini: activities relating to oil and gas drilling are believed to be increasing across the breeding range but not to be having any population-level impact (Brown et al. 2014). It has therefore been assessed as ‘local’ in recognition that it may be having some local impacts.
Note: disturbance arising from agriculture is assessed within threat ‘E. Impacts of agricultural on breeding habitats (including intensification, specialisation and disturbance’ for the reason that such disturbance events are linked to wider agricultural management practices, and so conservation actions designed to combat such disturbance are best considered within the context of wider farming actions. However, the information below is useful for considering the impact that disturbance from farming activities exerts on populations. The same is true for disturbance which only occurs due to other threats e.g. peat extraction, wind turbines. A variety of human activities can result in increased levels of disturbance of breeding birds. Such disturbance exerts a direct influence on breeding activities as well as indirect influences on food supply (Boschert & Rupp 1993) and may exacerbate the impact of other threats outlined in this section. For example, disturbance may result in higher rates of nest predation if, following a disturbance event that forces an incubating adult to leave the nest, crows return to the disturbed area faster than the incubating adult (Jensen & Lutz 2006). Alarm calls and other behaviours in response to disturbance could also alert predators to the whereabouts of nests and broods. Research in the Upper Rhine Valley, Germany highlighted the impact of human disturbance on breeding success. 30% of nest losses (39/131) were assigned to disturbance events, which encompassed agricultural activity, recreational activities, military use, predation and weather (Boschert & Rupp 1993). The flying of model aircraft and density of road traffic have been shown to have an impact on the nesting and feeding distribution of a breeding population (Boschert 1993). Failed breeding attempts due to high levels of public access to farmland have also been reported in Sweden, where dogs, horse riding and ATVs can pose a problem (Adriaan de Jong, pers. comm.). N. a. arquata: Eurasian Curlew nesting in the UK uplands have typically been associated with areas of low potential disturbance (Haworth & Thompson 1990) and large areas of the UK, Fennoscandia and Russia, which together host > 90% of the population, are likely to suffer relatively low levels of disturbance. Conversely, disturbance in Dutch moorland habitats by walkers and dogs is thought to be significant, whilst recreational activities are perceived to be increasing within some Range States (e.g. Denmark, Estonia, Austria, Poland). This threat has been assessed as ‘local’, in recognition that large portions of the population may be subject to relatively low levels of disturbance, but that disturbance can have a particularly large impact locally. N. a. orientalis and N. a. suschkini: levels of disturbance are increasing within the breeding ranges of both subspecies and this threat is considered by experts to be having a population-level impact (Brown et al. 2014). They have therefore been assessed as ‘local-medium’.
Research suggests that the impact of wind turbines on breeding populations may vary between sites. Research at an upland site in Scotland found that birds demonstrated clear turbine avoidance (Pearce-Higgins et al. 2009). Conversely, research at a lowland site in Germany found no evidence of wind turbines impacting on the overall population trend for the site; however, there was weak evidence that suggesting turbines had a displacement effect up to 200 metres (Reichenbach 2001). N. a. arquata: The construction of wind turbines coincides with breeding habitats in several Range States (e.g. Ireland, Germany, UK) and whilst the evidence suggests different populations might respond differently, expert opinion is that wind turbines are likely to have a population-level impact, especially in the future as increasing numbers of wind farms are constructed within breeding areas. As such, this threat has been assessed as ‘medium’ with the acknowledgment that further research is required (see Section 4. Framework for action). N. a orientalis & N. a. suschkini: This threat is not considered by experts to be having an impact on the breeding grounds of either population (Brown et al. 2014). It has therefore been assessed as ‘low’.
Climate change predictions are associated with an increase in the frequency and intensity of severe weather events, including flooding and droughts. Both have the potential to impact negatively on habitat quality and productivity, particularly cold, wet weather conditions that occur during the breeding season; if sustained for over 24 hours then chicks are susceptible to starvation or hypothermia (Witt 1989, Beintema & Visser 1989). There are examples of flooding impacting on local populations; rising water levels has caused the total loss of key breeding habitats in the Volga River delta and in other coastal wetlands of the Caspian Sea (Saulius Svazas, pers. comm). The flooding of clutches is also the principle threat to breeding populations in the Pripyat River floodplain, Belarus and Nemunas River delta, Lithuania (Saulius Svazas, pers. comm). A changing climate may also impact on breeding habitats in a more subtle, gradual manner; a prolonged growing season across northern Europe, as a consequence of climate change, may result in earlier mowing dates and longer grazing periods which could result in reduced breeding success (David Schönberg Alm & Anja Pel, pers. comm). Recent modelling work, as undertaken in A Climatic Atlas of European Breeding Birds, has predicted that if current climate projections are realised, by the end of the 21st Century the simulated potential distribution of the Eurasian Curlew will have reduced by 40% and shifted north-eastwards (Huntley et al. 2007). All subspecies: there is already evidence of breeding habitat loss and deterioration as a result of climate change. This threat seems particularly apparent for populations that breed at low altitudes. Whilst quantifying the impact at population-level is not possible, it is likely that climate change will lead to both the immediate and sudden changes with consequence for local populations, as well as gradual changes that degrade habitat quality. As such, this threat has been assessed as ‘local-medium’ for all three subspecies. Threats present on non-breeding grounds
Eurasian Curlew are a game species across several parts of their non-breeding range. For certain populations, hunting may unintentionally target younger birds. For example, adult birds from Sweden mostly migrate to northwest Europe whilst juveniles and sub-adults migrate further down the Atlantic coast (Adriaan de Jong pers. comm.). It is also likely that juveniles are more vulnerable to hunting due to their inexperience. N. a. arquata: approximately 95% of the population overwinters in northwest Europe (Figure 3) with a small percentage migrating through into the Iberian Peninsula and West Africa, where hunting is thought to be minimal. The Eurasian Curlew is listed on Annex II, Part B of the EU Birds Directive, permitting hunted in listed Member States, stated as Denmark, France, Ireland and the UK. Hunting bans were subsequently implemented in Denmark, the UK (1982 for Scotland, England and Wales; 2011 in Northern Ireland) and Ireland (2012), whilst France implemented a 5-year moratorium on hunting in July 2008. However, in February 2012 the moratorium was partially lifted, allowing hunting at certain coastal sites from the first Saturday in August until the end of January (Mathieu Sarasa pers. comm.). The moratorium was extended for terrestrial sites and some coastal areas until 2018. The number of birds shot in France is unknown because prior to the moratorium, annual estimates of bag size were pooled with ten other waterbird species in surveys (ONCFS 2000). A posteriori inference suggested an annual bag size of approximately 7,000-8,000 birds prior to the moratorium in 2008 (Fouquet 2013). Anecdotal evidence suggests that annual hunting bag estimates were probably overestimated due to the sampling techniques and inferences used during the survey (Mathieu Sarasa pers. comm.). Either way, the current level of hunting in France is expected to be less due to the partial moratorium at terrestrial and some coastal sites, and an ongoing survey will provide updated estimates (Enquëte Nationale Tableau de Chasse ONCFS/FNC). At least 25,000-52,000 curlews were estimated to winter in France during 2010-2012 (Wetlands International & ONCFS 2010, 2011, 2012), with a peak of 80,000 during migration (Fouquet 2013). As mentioned earlier, Eurasian Curlew are hunted in certain regions of Russia. Whilst no bag data exists, they are not a popular quarry species, at least in the northern European Russia (Vladimir Morozov, pers. comm.). The level of hunting in southern European Russia is currently unknown. The situation regarding hunting in parts of eastern Europe (Belarus, Ukraine and Romania) where Eurasian Curlew may pass through on migration in reasonable numbers, is also unknown. Overall, hunting pressure will have declined considerably across Northwest Europe in recent decades due to bans and moratoria. However, whilst the numbers of birds shot in France is likely to be less than 1% of the total population, the impact of this harvesting on the total population and the portion of the population that overwinters or migrates through France en route to Iberia and West Africa, is currently disputed. N. a. orientalis: Hunting may occur around the Black Sea, but no data or information is currently available (Vladimir Morozov pers. comm.). In Iraq, the average annual hunting bag is approximately 200-300 birds, which occurs mostly in the south (Mudhafar Salim, pers. comm.). Overall, there is insufficient data to enable an adequate assessment for the entire range. It has therefore been assessed as ‘unknown’ with the acknowledgment that further research is required (see Section 4. Framework for Action). N. a. suschkini: the non-breeding range of this subspecies is currently unknown and therefore an assessment of this threat is not possible at this stage.
N. a. arquata: There is not thought to be any illegal killing or taking of birds across Europe or much of West Africa, although illegal killing is thought to be increasing in Tunisia (Claudia Feltrup-Azafzaf, pers. comm.). There are some information gaps concerning the legal status and level of hunting and/or illegal killing in some Range States in eastern Europe. Since illegal hunting is not thought to be occurring in NW Europe, Iberia and other parts of West Africa, it is probable that the impact on the population is low but confirmation of the situation in eastern Europe is needed to be certain. N. a. orientalis: In Yemen, waders are increasingly being indiscriminately trapped by falcon trappers using mist nets at coastal sites to feed falcons; whilst no data exists, it is likely this includes Eurasian Curlew (David Stanton, pers. comm.). No information has been made available regarding illegal killing (nor legal hunting) of passage birds in the eastern Mediterranean or the Middle East; indeed, the legal status of Eurasian Curlew within the Range States of these regions is largely unknown. The impact of illegal killing is therefore unknown. N. a. suschkini: the non-breeding range of this subspecies is currently unknown and therefore an assessment of this threat is not possible at this stage.
Pollution of non-breeding habitats can arise from several different sources (e.g. oil, toxic substances, plastic garbage, agricultural run-off, etc). Such pollutants have the potential to impact on Eurasian Curlew through both direct effects (e.g. the digestion of a pollutant resulting in a reduction in fitness, or mortality) and indirect effects (e.g. by negatively impacting on the invertebrate food chain). Whilst oil spills can have disastrous impacts on marine and coastal habitats, most oil pollution comes from regular shipping traffic (Hötker et al. 2010). As is the case on breeding grounds, there have been no studies investigating the impact of different pollutants present at wintering sites on adult and juvenile survival, or the impact they may have on subsequent breeding success. Evidence from studies of Snipe Gallinago gallinago (Beck & Granval 1997) suggest that ingestion rates of lead shot in some wader species may be as high as amongst wildfowl, but there have been no specific studies on Eurasian Curlew (Jensen & Lutz 2006). There are concerns regarding the impact pollutants are having at important wintering sites, with anecdotal evidence suggests pollution from a variety of sources (including industrial effluents, domestic waste and urban run-off) is increasing in the Gulf of Gabès, Tunisia (Claudia Feltrup-Azafazaf, pers. comm.), whilst a slow but significant deterioration of habitat due to pollution is expected to be occurring at The Banc d'Arguin National Park in Mauritania (BirdLife International 2014). Pollution of coastal sites is occurring in Yemen due to increasing agricultural run-off and the accumulation of heavy metals due to sewage outflows (David Stanton, pers. comm.) and is also increasing at non-breeding sites in Turkey, although is localised and the impact is unknown (Kiraz Erciyas-Yavuz, pers. comm.). Wetland sites used by Eurasian Curlew in southern Iraq are potentially threatened by widespread oil drilling activities as well as the resulting smoke produced from the extraction units (Mudhafar Salim, pers. comm.).
Disturbance at non-breeding sites can affect waterbirds both during feeding and roosting, especially at high-tide roosts (Burton et al. 2002). Eurasian Curlew are one of the most ‘nervous’ waders on their wintering grounds (Davidson & Rothwell 1993) with escape flight distances amongst the greatest of any intertidal feeding wader (Smit & Visser 1993). However, this is highly site-dependent and related to hunting intensity (Fitzpatrick & Bouchez 1998). Disturbance itself can be caused by a variety of recreational and commercial activities. Dutch studies show them to be sensitive to walkers and low-flying planes near high tide roosts: a reduction of 10% available foraging time was recorded in response to aeroplane traffic (Jensen and Lutz 2006). A UK study found curlew use of intertidal mudflats was significantly lower when within 200m of footpaths and when within 25m of roads (Burton et al. 2002). In Spain, an experimental disturbance study found that many birds would change site completely if flushed by a single walker. This led to a 51.2% reduction in the population using the site at mid-tide, and an 83.9% reduction when the disturbance occurred at high-tide. The disturbance treatment had no effect in reducing the number of individuals within the experimental area during low-tide (Navedo & Herrera 2012). N. a arquata and N. a. orientalis: Human disturbance at coastal sites in Turkey is widespread (Kiraz Erciyas-Yavuz, pers. comm) and increasing levels of disturbance at coastal sites has also reported across the Middle East (Brown et al. 2014). Increased disturbance caused by expanding human activity has been identified as a medium-level threat in the Bijagós archipelago (BirdLife International 2014a) and increasing levels of disturbance is thought to be occurring at staging and wintering sites in Ireland, Sweden and Denmark. Conversely, at a population level, the wintering population of N. a. arquata in NW Europe has increased in recent decades (Figure 2); a period coincident with site protection under the Birds and Habitats Directives. Disturbance is perceived to be increasing in some Range States and has been shown to impact on the foraging and roosting behaviour of Eurasian Curlew. However, the impact on daily energetic balances and individual survival rates has not been investigated. In addition, significant proportions of national wintering populations are within the Natura 2000 network, affording enhanced protection from threats including disturbance; for example, 32.8% of the UK’s wintering population is within the SPA network (David Stroud, pers. comm.). Overall, this threat has been assessed as ‘unknown’ for both subspecies as there is no way of quantifying the impact of disturbance on the population. N. a. suschkini: the non-breeding range of this subspecies is currently unknown and therefore an assessment of this threat is not possible at this stage.
Suction dredging of shellfish species not only depletes the target species but also disrupts sediments and severely disrupts benthic invertebrate communities. This can impact on bird species dependant on benthic communities for extended periods of time (Duriez et al. 2012, Ferns et al. 2000). At a long-term study site in the UK, mechanized cockle harvesting in 1996 reduced apparent survival from 95% (best data estimate: se=0.07) to 81% (se=0.19) for two years, and was correlated with a published analysis showing reduced survival in Oystercatchers Haematopus ostralegus (Taylor & Dodd 2013). Dredging for Brown Shrimp Crangon crangon in the Wadden Sea alters benthic communities and some species, such as Sabellaria worms, do not recovery following intensive dredging activity (Hötker et al. 2010). Dredging of Blue Mussel Mytilus edulis beds severely impacts on the flora and fauna associated with subtidal and intertidal mussel beds; curlews often feed on invertebrates within the mussel beds (Hötker et al. 2010). N. a. arquata: whilst studies have shown the impact shellfisheries can have in reducing Eurasian Curlew survival, with ~95% of the wintering population found in Northwest Europe, where there is an extensive network of protected sites, the scale of this threat is likely to have declined in recent decades. As such, it has been assessed as ‘low’. Shellfisheries are likely to be having a negative impact on the segment of the population that winters in West Africa alongside N. a. orientalis (see below). N. a. orientalis: large-scale fishing and harvesting of aquatic resources is leading to moderate-rapid habitat degradation in the Banc d'Arguin National Park, Mauritania (BirdLife International 2014b). Similarly, small-scale subsistence harvesting is happening across a large area of the Bijagós archipelago that the cumulative impact has been assessed as ‘high’ in a threat assessment for the site (BirdLife International 2014a). There is currently insufficient information regarding the scale of shellfisheries within other parts of the range to make an informed assessment. This threat has therefore been assessed as ‘unknown’. N. a. suschkini: the non-breeding range of this subspecies is currently unknown and therefore an assessment of this threat is not possible at this stage.
Increasing drought periods in certain parts of the range could lead to degradation or loss of important staging sites. This has been reported in the Volga region of Russia, where steppe wetlands have been lost over a period of 5-7 years (Vladimir Morozov pers. comm.). Water shortages are increasing in Iraq and could have an impact (Mudhafar Salim, pers. comm.). Sea levels are predicted to rise by up 56 cm by 2100 (International Panel on Climate Change). If natural processes were unhindered, intertidal and supratidal habitats would be expected to gradually ‘move’ inland as a result of sea level rise. However, in many coastal areas the presence of sea defence structures (i.e. sea walls) constrain and prevent this from happening, resulting in the loss of coastal habitats (‘coastal squeeze’). In the long-term, this has implications for roosting and feeding habitat, however the ability for populations to alter their wintering range towards more suitable sites, whilst largely unknown, is likely to occur. N. a. arquata and N. a. orientalis: degradation and loss of vital stopover and staging habitats is already being reported. Whilst it is impossible to quantify the impact, loss of important staging sites for a highly-migratory bird cannot be understated. It is likely that there will be further large-scale local impacts similar to the situation in the Volga region, alongside more gradual degradation of wintering habitats. At the same time, climate change may result in distributional shifts as birds adapt and take advantage of new sites as they become more suitable. As such, this threat has been assessed as ‘local-medium’. N. a. suschkini: the non-breeding range of this subspecies is currently unknown and therefore an assessment of this threat is not possible at this stage.
Increasing coastal development (for golf courses, marinas, hotels, real estates, recreation, industrial developments) is the primary reason for declines in the intertidal habitats used by Eurasian Curlew on the Arabian peninsula (Porter et al. 2008). Aquaculture developments pose an additional threat in some areas (David Stanton, pers. comm.). N. a. arquata: as with several other threats, with a reasonable proportion of the wintering population found within the Natura 2000 network, it is likely that important sites will be protected from such developments, and therefore any impacts are only likely to be ‘local’. N. a. orientalis: there is far greater development pressure at wintering sites, and this is known to be having an impact (Porter et al. 2008). Whilst insufficient data exists to quantify the impact, so it has been assessed as ‘unknown/medium’ since coastal development is increasing across wintering grounds in the Middle East and Africa (Brown et al. 2014). N. a. suschkini: the non-breeding range of this subspecies is currently unknown and therefore an assessment of this threat is not possible at this stage.
No research has been undertaken that has investigated the impact of drainage on staging or wintering birds. The impact could theoretically be large, if for example it occurred at an important staging site. N. a. arquata: drainage is not thought to be an issue for the wintering population in NW Europe, which accounts for approximately 95% of population. It could have local impacts, and has been assessed as such. N. a orientalis: There are several areas where drainage of non-breeding is occurring, for instance in Uzbekistan, where staging sites are being lost as a result of land conversion to agriculture (Elena Kreuzberg, pers. comm.). Overall, the extent and therefore impact drainage at staging, stopover and wintering sites is unknown. N. a. suschkini: the non-breeding range of this subspecies is currently unknown and therefore an assessment of this threat is not possible at this stage. Low productivity Reduced adult survival Chick mortality Nest destruction Climate change (prolonged wet periods) Reduced adult fitness? Increasing predation Disturbance Pollution Figure 2. Problem tree for the Eurasian Curlew, on breeding grounds and non-breeding grounds.
Population declines
Drainage Coastal Development Recreation Agricultural operations Depleted prey base Loss, degradation and fragmentation of non-breeding habitats Adult mortality Reduced adult survival Reduced adult fitness? Human disturbance Pollution
Agricultural operations NON-BREEDING GROUNDS BREEDING GROUNDS 3. POLICIES AND LEGISLATION RELEVANT FOR MANAGEMENT 3.1. International conservation and legal status of the species The status of the Eurasian Curlew under the main international legislative instruments for conservation is summarised in Table 5. Table 5: International conservation and legal status of the Eurasian Curlew.
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