Since 1986, seabird populations in the UK and Ireland have been monitored through the Seabird Monitoring Programme coordinated on behalf of partnership organisations by JNCC. Sample data on breeding abundance and breeding success of seabirds are collected from a large network of sites, both regionally and nationally, to enable species’ conservation status to be assessed. To examine trends at individual colonies, at country level and across the whole UK, it is essential that individual sites can be monitored consistently for many years. Data on breeding abundance – the number of breeding pairs or individuals – provide a medium to long term measure of how populations are faring. Data on breeding success/productivity – the number of chicks fledged per breeding pair – are regarded as short term or more immediate measure of population status. Studies at four key sites (Isle of May, Canna, Fair Isle and Skomer) provide information on adult survival, diet, phenology used to help to diagnose the changes in abundance. Additional information on survival rates at other sites is collected through the BTO’s Retrapping for Adult Survival (RAS) scheme (Horswill et al. 2016), although there are no current RAS sites in Northern Ireland. The SMP generates annual indices of abundance and breeding success from these data which are expressed as a percentage of the population recorded at sites in 1986 when standardised monitoring began (JNCC 2016). Where possible trends are given at the scale of the UK or country level, but where coverage is only possible at individual sites, the indices are shown at the site level. The SMP is a vital programme for monitoring seabird population trends between the full national censuses.

Number of coastal Herring Gull populations have reduced markedly in recent years. The breeding gull colony of the South Walney and Piel Channel Flats Site of Special Scientific Interest (SSSI), within the Morecambe Bay and Duddon Estuary potential Special Protection Area (pSPA), is of national and intermational importance for its number of Herring Gull Larus argentatus and Lesser Black-backed Gull Larus fuscus.

This annex to BTO Research Report 694 (Clewley et al. 2016) presents a summary update for 2017 on the results of a GPS tracking study of Lesser Black-backed Gulls Larus fuscus breeding in the Bowland Fells Special Protection Area (SPA).

Over the past 50 years there has been widespread improvement in water quality in many freshwater and coastal systems driven by domestic and European legislation, most recently the EU Water Framework Directive (EC Directive 2000/60/EC), but also including the Urban Waste Water Treatment Directive (EC Directive 91/271/EEC) and Bathing Water Directive (EC Directive 76/160/EEC).

Large-scale population estimates of species are used for several reasons, including the assessment and protection of important sites. However, determining a national population requires extensive surveying and using methods that allow counts to be scaled up to the number of birds actually present and across a larger area. This new BTO study looks at different methods used to estimate the population of Nightingales in the UK. Nightingales have declined by 61% in the last 25 years and therefore determining which sites contain the largest populations is vital. The study focused on 2733 2x2 km squares, 2356 where Nightingales were known to be, as well as randomly-chosen squares whose selection was stratified based on habitat suitability. By using different analytical methods, the final population was estimated to be between 5094 and 5938 territorial males, of which only 55-65% were counted during the surveys. It is therefore important to consider how to fully control for variability in detection and for birds outside of surveyed areas when estimating national populations. The study also highlighted the importance of Lodge Hill SSSI for breeding Nightingales, which was designated for its nationally important population of the species, based on the results presented in this paper.

Initial findings suggest that Lesser Black-backed Gulls in north-west England fly within wind farms, but may avoid wind turbines once there. Offshore wind farms may affect birds in many ways, such as stopping them moving between places, or restricting access to areas where they feed. Collision risk is a key concern for seabirds, yet there has been little study to date of the use of wind farms by birds from known breeding colonies. This study, led by BTO, provides a first look at the movements of Lesser Black-backed Gulls at a colony in north-west England and their interaction with five operational offshore wind farms. The birds were tracked with GPS tags which recorded location, speed and height. Out of the 24 birds tracked, 15 visited wind farms, and in total spent 1.3% of their time there. A detailed look at the movements of two birds that visited wind farms most often, showed that their flight heights were greater within wind farms than outside, particularly during the day, potentially placing them at greater risk of collision. However, within wind farms, their use of the zone swept by the rotor blades was significantly less than expected. Although preliminary, these results suggest that Lesser Black-backed Gulls at this site may not avoid wind farms, but could avoid individual wind turbines once inside the wind farms. Further work is now being conducted to verify these patterns, which will be important in improving our understanding of the likely collision risk for seabirds.

The BirdTrends 2017 report is a one-stop shop for authoritative information about the population status of the common breeding birds of the wider UK countryside. The report is based on data gathered by the many thousands of volunteers who contribute to BTO-led surveys.