Changes in the Uists wader populations: the importance of agricultural practices and vegetation
The Uists in the Western Isles are home to a rare habitat known as “machair”, which supports exceptionally large breeding populations of waders, particularly Dunlin, Lapwing, Redshank, Ringed Plover, Oystercatcher and Snipe. There is strong evidence that egg losses to Hedgehogs, which were introduced in the 1970s, have been responsible for declines in some of these populations. However, declines have also been recorded in areas not colonised by Hedgehogs, and some increases since 2000 have occurred at sites known to support high numbers of Hedgehogs, suggesting other factors might also be at play.
A new study by the BTO and the James Hutton Institute investigated the role of changes in vegetation and agricultural practices using data spanning three decades. Numbers of Oystercatcher and Redshank have increased during this time, while those of Dunlin and Ringed Plover have fallen, and Lapwing has remained stable. There were also changes to machair cultivation - the area of land cultivated was the same, but the habitat mosaic created had become simpler and more homogeneous, with deeper ploughing and a greater reliance on inorganic fertilizers instead of the traditional practice of using seaweed. Reductions in Dunlin and Ringed Plover were smallest where soil fertility and machair cultivation had changed the least. In contrast, Oystercatcher numbers rose on less fertile soils. The interaction between vegetation changes, disturbance and predation pressures by Hedgehogs and other species must now be investigated to inform how to conserve the Uists' nationally important breeding wader populations.
BTO reports on plans for the Thames Estuary airport
BTO ecologists have recently reported on controversial proposals to build an airport on the Isle of Grain in the Thames Estuary. This development would cause significant loss of coastal habitat within two areas that are protected under European law for their internationally important waterbird populations.
Spring conditions in the Mediterranean affect migrants breeding in the UK
Migrant birds are vulnerable to climate change because they can be affected by conditions on their breeding grounds, wintering grounds or passage areas in between. Many long distance migrants are in severe decline, and previous BTO work has shown this can be related to changing conditions in Africa, as well as to conditions on British breeding grounds. BTO research published last year showed that although conditions in Africa can ‘carry-over’ and affect the timing of nesting in this country, the most important factor influencing breeding was spring temperature in the UK.
A new study by the BTO and the University of Sheffield builds upon this work by considering the impacts of climatic variation in passage regions, as well as the breeding and non-breeding grounds. It focuses on three declining migratory species of regional conservation concern in Europe - Redstart, Wood Warbler and Spotted Flycatcher. Long-term data from the Nest Record Scheme revealed that the strongest factor influencing timing of breeding was temperatures in the Mediterranean during spring migration, with warmer conditions leading to earlier breeding. The work has important implications for the conservation of these declining species and emphasises the importance of conditions during spring passage.
Patchy habitats expose woodland birds to winter weather
Projected climate change impacts on the populations and distributions of species pose a challenge for conservationists. In response scientists and policy makers have proposed a number of management strategies to enable species to persist in a changing climate. However there is limited evidence to support these management interventions, making it difficult for conservationists to decide on the most appropriate action to take for different circumstances.
New BTO-led research has supported the prediction that habitat attributes (woodland patch isolation and area of woodland at the site and at the wider landscape scale) may influence the ability of some woodland bird species to withstand weather-mediated population declines. Results suggest that these effects were most apparent among generalist species, such as Bullfinch and Robin. However several specialist species, like Nuthatch and Willow Tit, were also more likely to increase following population decline where there was more woodland at the site and in the wider landscape. While management is unlikely to provide a universal benefit to all woodland species, landscape-scale conservation initiatives that maximize woodland patch size and minimize patch isolation may improve the resilience of some woodland bird populations to climate change.
Climate change disrupts natural relationships between species
Change is altering species’ distributions and populations but it is unclear how these impacts occur. New research led by the BTO reviewed almost 150 published studies to show that the main impacts of climate change occur through altered interactions between species within an ecosystem, rather than direct responses to climate. Each species shares an ecosystem with other species, some of which it might eat, and others that might eat or compete with it. This study found it was changes to the populations or activity of these other species that were responsible for many of the impacts observed. For example, upland birds such as the Golden Plover are affected by increasing summer temperatures, which cause problems for their Cranefly prey.
Much conservation action is concerned with managing species’ populations, so the conservation tools to reduce the impacts of climate change are already available and vulnerable species can be helped to adapt. Degraded peatland habitats in the UK uplands could be restored, for example, boosting Cranefly populations, and increasing their resilience to climate change. This study highlights the need to consider the complex ecological relationships between species when assessing the impacts of climate change at a global scale.