SocLap sap – working draft

Predation levels can be influenced both directly and indirectly by human activity. Nest predation of a group of wading birds in Western Europe, including Eurasian Curlew, has increased 4-fold over the last four decades (Roodbergen et al. 2012). Populations of several avian and mammalian predators of nests and chicks have increased in recent decades (Roos et al. 2012). Factors responsible for these increases include: decreasing levels of predator control for sporting or farming reasons (e.g. leading to increased Red Fox Vulpes vulpes and crow Corvid spp. populations); the introduction and subsequent range expansion of non-native species (e.g. Racoon Procyon lotor, Racoon Dog Nyctereutes procyonoides, American mink Neovison vison); and the recovery of depleted populations following the introduction of environmental legislation (e.g. recovery of raptors following the DDT ban, protected status of Badgers Meles meles in the UK).

Landscape and habitat variables may also influence predation pressure by benefitting predators and/or their hunting strategies. The conversion of rough grazings into improved grasslands may have increased food supplies for mammalian and avian predators through increasing the availability of carrion and soil invertebrates (Grant et al. 1999) whilst uniform grass swards and reduced habitat heterogeneity may increase the ease with which predators locate nests and chicks (Grant et al. 1999, Valkama et al. 1999). Predation of Eurasian Curlew nests and chicks has been found to be higher in fragmented landscapes (Valkama et al. 1999). Finally, lower nesting densities in increasingly fragmented landscapes may also result in a reduction in the effectiveness of communal nest defence of waders (Valkama et al. 1999).

The main predators of nests and chicks have been shown to vary in different geographic areas. Where medium-sized mammalian predators are present (Red Fox Vulpes vulpes, European Badger Meles meles, Racoon Procyon lotor, Racoon Dog Nyctereutes procyonoides) they appear to depredate the majority of nests and chicks (Grant et al. 1999, Valkama et al. 1999, Berg 1992b). In the absence of medium-sized mammalian predators (e.g. on islands) high levels of predation may still occur through avian predators (Grant et al. 1999). A study in the UK uplands found an almost significant (p=0.08) negative correlation between Common Raven Corvus corax abundance and Eurasian Curlew abundance, implying further research is required to better understand whether ravens are contributing to Eurasian Curlew declines (Amar et al. 2008).

In a UK study area containing low Fox and Crow densities due to intensive predator control for Red Grouse Lagopus lagopus scotica shooting, the Stoat Mustela erminea was identified as the main predator of Eurasian Curlew nests and chicks (Grant 1997).

The relative impact of different predators therefore appears to be site-specific, and the absence or reduction of one predator species may result in higher levels of predation from others. The interactions between different predators are highly complex. In some landscapes the reduction or removal of a top predator in an ecosystem (e.g. fox) may lead to a surge in the population of medium-sized predators (e.g. stoat) resulting in an overall increase in the predation of vulnerable prey species: a process known as mesopredator release.

An increasing number of studies are assessing these complex interactions and evaluating the impact of predator control as a potential management tool for increasing the productivity of ground-nesting birds. An experimental study in the UK uplands found that the control of Carrion Crows, small mustelids and Red Foxes resulted in a 3-fold increase in Eurasian Curlew nesting success and a significant increase in the number of Eurasian Curlew (Fletcher et al. 2010). Whilst the impact of Foxes, Badgers, Racoons, Racoon Dogs, mustelids and possibly Ravens can have an impact on Eurasian Curlew breeding success and population numbers, research has shown no population level impact of adult and sub-adult predation by birds of prey e.g. Peregrine Falcon Falco peregrinus (Amar et al. 2008).

In certain locations (e.g. northern Fennoscandia) the influence of human predator management on mesopredator abundance is far more localised and less influential; mesopredator populations are driven by other factors such as vole cycles (de Jong, pers. comm).

N. a. arquata: The impact of this threat has been assessed as ‘Critical’ with a high degree of confidence. Modelling by Grant et al. (1999) predicted that the productivity levels recorded at a mainland study site⁵ would lead to a decline of 25-40% over a 6-year period, which would be sufficient to account for the 25% observed population decline in Northern Ireland between 1986 and 1992 (i.e. a 6-year period). Extrapolating, such a rate of decline would exceed 30% over a ten-year period. Since predation was the overwhelming source of nest and chick mortality in this study, and that high levels of nest and chick predation have been recorded in numerous study populations (Valkama et al. 1999, Berg 1992b, Boschert 2004, 2005) and is increasing across much of Europe (Roodbergen et al. 2012), predation of nest and chick predation is likely to be causing very rapid population declines (>30% over 10 years).

N. a. orientalis: insufficient information is available to make an assessment on this threat. It has therefore been assessed as ‘unknown’.

N. a. suschkini: insufficient information is available to make an assessment on this threat. It has therefore been assessed as ‘unknown’.

B. Nest destruction and increased chick mortality due to agricultural operations (including mowing, trampling and burning)

arquata: medium-high orientalis: unknown/local suschkini: unknown

Eurasian Curlew nest and rear their broods in a variety of agricultural grasslands and crops. Nests and chicks are therefore highly susceptible to farming operations that take place during the breeding season.

In areas where birds nest in arable crops, operations such as ploughing, harrowing, sowing, rolling and spraying could all destroy nests. Harvesting typically takes after the breeding season. Studies from Sweden have shown that of the small number of nests that occur in spring-sown cereals, a proportion of nests are destroyed by operations (see section 1.7.4) whilst a study in Lower Saxony, Germany found that farming operations destroyed all nests in arable fields (Tuellinghoff & Bergmann 1993).

Agricultural grasslands include permanent pastures, grass leys (temporary grass fields within an arable/grassland rotation), meadows and rough grazings. The management and timing of operations can vary greatly between these grasslands, but operations such as rolling and cutting can result in nest destruction and chick mortality, as too can trampling by livestock.

A study in the UK found tramping by cattle accounted for 20-33% of nest failures (Grant 1997). The impact of nest trampling is associated with the stocking density and livestock used (Green 1985). In parts of Germany, considerable effort is put into chick protection schemes during mowing periods (Natalie Busch, pers. comm.).

New EU agricultural regulations require some form of agricultural activity to occur for the payment of agricultural subsidies, including on fallow land. Where such activities take place during the nesting and chick-rearing period they may have impacts on the breeding success of ground-nesting birds. Whilst Member States have reduced the potential impact by prohibiting agricultural activity for a period during the summer (e.g. 1 March to 30 June in Sweden) some losses could still result from these policies (David Schönberg Alm, pers. comm.).

Whilst the burning of abandoned grasslands is thought to be increasing in European Russia, it is not expected to be having a population-level impact (Vladimir Morozov, pers. comm.). The burning of grasslands to encourage fresh growth for livestock also occurs on breeding grounds in parts of Siberia, and when undertaken during the breeding season this can obviously destroy nests and chicks. However, since land abandonment is also increasing across European Russia (Vladimir Morozov, pers. comm.) it is possible that burning abandoned grasslands might actually provide overall benefits by preventing scrub formation and maintaining habitat diversity e.g. through creating short grassy areas for feeding.

In summary, studies have shown that agricultural operations do result in nest destruction and chick mortality across a suite of agricultural habitats (upland pastures, lowland wet grassland, spring cropping) and across the range.

N. a. arquata: This impact is likely to vary considerably across the breeding range, due to variation in preferred nesting habitats and the agricultural management they are subject to. This threat appears to be particularly prevalent at southern latitudes, where birds nest in more intensively managed grasslands. Overall, this threat has been assessed as Medium-High, recognizing that in some Range States (e.g. the Netherlands) it may be High-Critical.

N. a. orientalis: The general decline in all forms of farming activity across the breeding range (Brown et al. 2014) suggest that nest and chick losses to agricultural activity are probably decreasing across the breeding range as a whole. It will is still likely to be a factor at certain sites. It has therefore been assessed as ‘unknown/local’.

N. a. suschkini: insufficient information is available to make an assessment on this threat. It has therefore been assessed as ‘unknown’.

C. Mortality caused by hunting on breeding grounds

arquata: absent-low orientalis: medium-high suschkini: medium-high

For a long-lived species with low productivity, Eurasian Curlew populations are especially sensitive to adult mortality (Jensen & Lutz 2006).

N. a. arquata: No hunting occurs on breeding grounds within EU member states, nor in Norway, which together account for 61-77% of the breeding population. Information on hunting in Belarus is lacking. Eurasian Curlew are a game species in regions of Russia, but the open season occurs mostly outwith the breeding season (early August to December) and the species is not popular quarry. Whilst some gaps in information exist, it is unlikely that hunting on breeding grounds is impacting on the population. It has therefore been assessed as ‘absent-low’.

N. a. orientalis & N. a. suschkini: Expert opinion is that hunting pressure has increased considerably across parts of the both subspecies’ breeding ranges in recent years, and whilst there is no statistical or published evidence to support this, experts believe it to be having a negative impact on the population (Brown et al. 2014). It has therefore been assessed as ‘unknown/medium-high’.

D. Mortality caused by illegal killing on breeding grounds

arquata: absent orientalis: unknown suschkini: unknown

N. a. arquata: Illegal killing and collecting is not thought to occur at any detectable level on European breeding grounds nor in European Russia. It has therefore been assessed as ‘absent’.

N. a. orientalis: Eurasian Curlew are a game species only in certain regions of Russia; they are protected in other regions. Illegal killing and collecting was not highlighted as an issue in a recent review of all Numenius spp. (Brown et al. 2014). It has therefore been assessed as ‘unknown’.

N. a. suschkini: Insufficient information is available to make an assessment on this threat. It has therefore been assessed as ‘unknown’.

E. Impacts of agricultural on breeding habitats (including intensification, specialisation and disturbance)

arquata: critical orientalis: low suschkini: low

Recent decades have seen large-scale agricultural improvements (e.g. drainage, reseeding with more agriculturally productive grasses, increased fertiliser rates, etc) across a large proportion of the breeding range. Grasslands subject to such management typically result in a homogenous habitat (i.e. a uniform sward structure with low plant species diversity). Such grasslands are fast-growing, allowing earlier and more frequent mowing compared to semi-natural or agriculturally unimproved grasslands (Baines 1989, Donaghy & Mellon 1998). Low plant species diversity combined with frequent cutting reduces the diversity of surface-dwelling invertebrates, which are an important source of food later in the breeding season (Berg 1993). It is important to note that improved grasslands can provide high-quality foraging grounds for adults when part of a mosaic of wetlands and varying grassland habitats (e.g. Ewing et al. 2012); the problem arises when improved grassland dominates agricultural landscapes.

The impact of a reduction of grassland habitats in arable landscapes (i.e. areas where cropping is the dominant land use) that support breeding populations has been documented in parts of Finland (Tiainen 2001, Tiainen & Pakkala 2001), southern Sweden (Berg 1992), and the upper Rhine Valley, Germany (Boschert 2004, 2005). Similarly, in grassland-dominated landscapes, the loss of arable fields may cause a reduction in quality of breeding habitat (de Jong 2012).

Wetland habitats are a key component of breeding habitat. Drainage is a management practice used to increase agricultural production (it increases the growth rate of crops and grass and reduces the susceptibility of livestock to certain diseases such as liver fluke) and can include both the maintenance of existing field drainage systems (often a requirement of EU cross compliance) as well as new field drainage systems. Political pressure from the agricultural sector to provide grant support for land drainage continues (e.g. NFUS 2014). The method of drainage is important as certain drainage systems (e.g. overland drainage systems or ‘footdrains’) can improve the quality of breeding habitat (e.g. Smart and Coutts 2004), and replacing such systems with underground drainage systems leads to habitat degradation and population decline. For example, in northern Sweden, the majority of Eurasian Curlew breed on well-drained farmland, but densities have dropped in response to open ditches being replaced with underground drainage systems (Adriaan de Jong, pers. comm.).

N. a. arquata: Large-scale changes in farming practices that have had negative consequences for farmland breeding habitats have occurred across much of breeding range in recent decades, and continues today. Evidence quantifying the overall scale and population-level impact on Eurasian Curlew populations isn’t available, but many of the farming practices outlined above clearly result in the loss and degradation of breeding habitat, and are evident across a large proportion of the range. It has therefore been assessed by experts as ‘Critical’.

N. a. orientalis: Large-scale changes in farming practices (excluding land abandonment which has been assessed separately) is not considered to be having a population-level impact due to a general trend of reduced farming activity across Siberia (Brown et al. 2014). It has therefore been assessed as ‘low’.

N. a. suschkini: Experts believe that whilst there has been an increase in the scale and intensity of cropping in recent decades across the breeding range, it is not resulting in any impact on the population (Brown et al. 2014). It has therefore been assessed as ‘low’.

F. Land abandonment on breeding grounds

arquata: unknown/medium orientalis: unknown/low suschkini: absent

Land abandonment can occur at a landscape, farm and field level. Decline in farming activity across large areas, driven by global economic and social trends, has occurred in regions of northern European Russia and Scandinavia (Vladimir Morozov, Adriaan de Jong, pers. comm.), resulting in ecological succession taking place; breeding habitats sustained by farming will revert to coarse grasslands then ultimately scrub and forest. In such landscapes, breeding areas have become restricted to peatlands and meadow floodplains (Vladimir Morozov, pers. comm.). In some eastern European Range States (e.g. Lithuania), the collapse of the Soviet agricultural scheme led to important farmland breeding habitats (e.g. alluvial meadows, fens) being undermanaged and degraded due to the development of rank grassland and scrub encroachment (Kurlavičius and Raudonikis 1999). Other examples include the Saone Valley, France (Broyer & Roche 1991), parts of the UK uplands and Västerbotten, Sweden, where abandonment was associated with population decline and range contraction (Adriaan de Jong. pers. comm.).

Whilst reversing such trends is impossible in certain regions, agricultural support schemes do exist to support the continuation of farming in certain areas. Where these are adequately resourced and targeted they may maintain breeding habitat.

Land abandonment may also occur at the individual farm level, whereby certain fields or areas are ‘undermanaged’ as production is increasingly focused on more agriculturally productive fields. Sometimes this under-management is exacerbated by agri-environment management (O’Brien & Wilson 2011). It is important that these undermanaged areas are sufficiently grazed and/or cut to provide breeding habitat; if the level of agricultural activity is too low then these fields may become dominated by tall, rank vegetation (e.g. Juncus spp.) and scrub.

N. a. arquata: Increasing land abandonment is reported to be occurring in several Range States (e.g. Russia, Sweden, Estonia, Ireland, UK) which together host approximately 62% of the population (based on tallying up mean national population estimates). However, it only affects certain regions within these Range States. Whilst the evidence base is poor and no quantitative data exists, since it is occurring over a reasonable proportion of the breeding range, and is expected to be having an impact where it does occur, the impact is likely to be greater than just ‘local’. For these reasons it has been assessed as ‘unknown/medium’.

N. a. orientalis: There is much less information available in terms of the scale of land abandonment, but expert opinion is that declining farming activity across Siberia is not likely to be having a population-level impact (Brown et al. 2014). It has therefore been assessed as ‘unknown/low’.

N. a. suschkini: large-scale land abandonment was not been reported to be occurring across the breeding range during a recent review (Brown et al. 2014). It has therefore been assessed as ‘absent’.

G. Loss and degradation of peatland habitats on breeding grounds

arquata: unknown/medium orientalis: unknown/ suschkini: unknown

Peatland habitats (e.g. lowland raised bog) are an important breeding habitat in several Range States. Anecdotal evidence from Germany and the UK suggests that Eurasian Curlew first began breeding on farmland after colonising farmland from adjacent bog habitats. In the future, peatland habitats may become increasingly important refuges in areas where farmland no longer provides suitable breeding habitat.

Peatland habitats can be degraded by several land management practices (Gunnarsson & Löfroth 2009) including peat extraction for fuel and horticultural products, overgrazing by livestock and native herbivores, burning and lastly drainage, which facilitates many of the other practices. Peat extraction typically involves peat being cut at the onset of the breeding season, so disturbance can be a secondary issue. Grazing and burning, when delivered at the appropriate intensity, can maintain a varied vegetation structure which benefits Eurasian Curlew and other species (Pearce-Higgins & Grant 2006). The wider environmental benefits, specifically relating to carbon sequestration and natural floodplain management, of restoring the hydrological function of peatlands has been increasingly well documented in recent years, resulting in several restoration projects.

N. a. arquata: more than half of the countries in Europe have lost 90% or more of their original natural peatlands (Wetlands International 2003). Whilst utilisation of peat and the subsequent degradation of peatland habitats still occurs across Europe, degradation is likely to be increasingly offset by large-scale peatland restoration projects that are occurring in several Range States (e.g. Belarus, Latvia, Lithuania, UK, Ireland) some of which are specifically targeted towards Eurasian Curlew (Saulius Svazas, pers. comm). No data is available to quantify the impact of this threat, but overall it is considered by experts to be having a negative impact on the population. It has therefore been assessed as ‘unknown/medium’.

N. a orientalis: insufficient information is available to make an assessment on this threat. It has therefore been assessed as ‘unknown’.

N. a suschkini: insufficient information is available to make an assessment on this threat. It has therefore been assessed as ‘unknown’.

H. Pollution on breeding grounds

arquata: unknown orientalis: unknown suschkini: unknown