This chapter discusses threats that are known or suspected to be having a negative impact on Eurasian Curlew populations. They include factors that are directly affecting population size through increased mortality of adults and chicks as well as factors that are indirectly affecting population size through loss of habitat, disturbance, etc. Threats have been assessed for each subspecies and have been made on the basis of severity (the impact on the population) and scale (the proportion of the population affected by the threat).
Several scientific studies have investigated threats acting upon Eurasian Curlew populations in Europe, both on their breeding grounds and on their wintering grounds. In such cases, the impact that threats have on the population is relatively well understood, supported by published scientific papers (i.e. experimental or correlative studies). Several studies have recorded productivity levels below those required for population stability, and there is consensus that breeding population declines are being caused by low productivity alongside the loss, degradation and fragmentation of breeding habitats. In the near future, there are concerns that senescence (an ageing population as a consequence of poor breeding success) may begin to exacerbate the trend of reproductive failure, and also lead to decreasing adult survival (Taylor and Dodd 2013). A summary overview of threats is provided in Table 4, followed by a description of each threat and an explanation of its rank, as set out below.