Latest Research

Gannets. Photograph by Jill Pakenham

Estimating seabird population size with uncertain species ID

Aerial surveys that capture high quality photos are increasingly being used to monitor bird populations, but these images are not always good enough to identify birds to species-level. A new study led by the BTO investigates how best to deal with this problem.

Great Skua tagging. Photograph by Angus Jackson

Scottish skuas in changing seas

Scotland has a large number of offshore sites where marine renewable developments (including wind, wave and tidal-stream installations) are proposed or under construction.The effect of these developments on marine ecosystems is not yet properly understood. Scotland is home to over 60% of the world’s breeding Great Skuas, and principal colonies are protected under the European Birds Directive. A new study led by the Environmental Research Institute and involving the BTO, has examined the potential effects of marine renewable developments on Great Skuas, using long-life GPS tags to reveal birds' movements throughout the breeding season and characterise their use of the marine environment.

Great Skua movements did not greatly overlap with areas of the sea where marine renewable developments are proposed. The largest overlap was with wave power installations, which are thought to pose a low risk to this species. However, the degree of overlap varied throughout the season and between colonies, with birds whose breeding attempts failed ranging over a larger area of sea than birds that were incubating or caring for chicks. Historical records of nest attendance also indicated that Great Skuas now travel further during the breeding season than in the past. Taken together, these findings show that assessing the potential impact of marine renewable developments on Great Skuas is complex. This long-lived species uses different parts of the marine environment at different times of the year, and might be flexible in choosing where to go depending on prevailing conditions. Tracking can help to assess the effect of planned marine renewable developments, but long term studies in conjunction with thorough monitoring are essential to fully understand the conservation implications for this and other seabird species.

Ringed Plover. Photograph by Ron Marshall

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.

Dunlin, photograph by Ron Marshall

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.

Wood Warbler. Photograph by Edmund Fellowes

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.