The nominate subspecies of Eurasian Oystercatchers Haematopus ostralegus ostralegus is the most abundant of all oystercatchers and the best studied. The main breeding and wintering areas are centered on the North Sea, but the distribution covers the European Atlantic coast to as far south as Ghana in western Africa. Population size increased strongly from the 1960s to 1990s to over one million birds. Although part of this expansion may have been caused by an ongoing successful adaptation to breeding inland, the main driving forces behind this increase are not well understood. Subsequently, the population size decreased substantially by about 200,000 individuals, mainly due to strong decreases in the Dutch-German-Danish Wadden Sea area. The decrease in the Netherlands is attributed largely to overexploitation by mechanical shell-fisheries; additional factors such as agricultural intensification and reduced eutrophication are likely to also have contributed. The causes for the decreases in Germany and Denmark are less well understood and urgently require further study. In other areas numbers are fairly stable or increasing, but good data for the Nordic countries are lacking. The global (and national) conservation status of H. o. ostralegus is classified as of ‘Least Concern’. We discuss other threats, such as habitat loss, climate change, hunting and human disturbance, and make prioritized recommendations for research and management.

The BirdTrends 2020 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.

New BTO research shows how data collected by an army of volunteer citizen scientists have been used to map bats in unprecedented detail. The Norfolk Bat Survey began in 2013, and represents a novel way of collecting high-quality and extensive data sets on the distribution and activity of bat species. The Norfolk Bat Survey was started in 2013 by BTO ecologist Stuart Newson. Stuart and his colleagues have taken advantage of advances in technology to map bat distributions, and activity on a scale never before seen. The Survey relies on a network of ‘Bat Monitoring Centres’ situated throughout the county, from which members of the public borrow passive bat detectors and set them up locally for three days at a time. Between 2013 and 2015, this cost-effective survey method generated over 1.2 million bat recordings, making it one of the most extensive high-quality data sets for bats from anywhere in the world and engaging volunteers with citizen science in the process. The project has improved our understanding of spatial patterns of bat distribution and activity of all species, from the near-ubiquitous Common Pipistrelle to the locally scarce Leisler’s Bat, increasing the number of records from Norfolk from 10 to almost 300. The study also reveals how bat activity varies through the night. For example, Common and Soprano Pipstrelles are most active shortly after sunset, when airborne small insect prey availability is at its peak, while Brown Long-eared Bats, which take prey from foliage are active throughout the night. On a seasonal timescale, several species have been found to disperse after breeding into areas that they are not reported from earlier in the season. Such information has important conservation implications. Surveys of many species of bat are required before land is developed. The techniques used by the Norfolk Bat Survey present a better way of carrying out such work, with more informative results. As more years’ data are collected, the technique will also allow changes in bat populations to be monitored in a way that has not previously been possible. The Norfolk Bat Survey has already been expanded into neighbouring parts of East Anglia by popular demand. In 2016, a new survey will also begin in southern Scotland using the Norfolk Bat Survey model, and we are discussing with BCT how this approach may inform bat monitoring more widely. This is an example of BTO research having a huge impact on our knowledge of the ecology of previously poorly understood species.