Capsule: The use of call-broadcasting significantly increases the number of Tawny Owls Strix aluco detected in winter point counts, but requires careful survey design to avoid introducing potential sources of bias into population estimates. Aims: To examine Tawny Owl response to call-broadcasting to aid survey design in national monitoring efforts. Methods: A nocturnal survey was undertaken at 36 survey points over three nights in winter in Thetford Forest, England. Each survey consisted of four consecutive five-minute segments: a passive count, followed by three counts with the use of call-broadcasting. Results: Few (4%) Tawny Owls were recorded during passive surveys, whereas the greatest response was during the first and second call-broadcast segments (49% and 36%, respectively). New detections declined to 11% in the final segment. Response was fastest at dusk, although time of night did not significantly affect the number of individuals detected. Male owls accounted for 79% of detections. Conclusion: Our results show that ten minutes of call-broadcast surveying will detect 85% of responsive Tawny Owls, thus vastly improving detection compared to passive listening alone. However, simultaneous counts of geographically separated detections should be used to provide a minimum count and reduce potential double-counting of mobile individuals.

The breeding populations of many different wader species are in decline across the globe, and the UK is no exception. These declines have been linked to increased predator numbers, changes in agricultural practices, and in the management of the wider landscape. There is an urgent need for information on how such changes in land management, particularly within farmland, may affect breeding waders. This information can then be used to inform future land management decisions. Long-term studies can make an important contribution to our understanding of wader decline, as is demonstrated by work carried out by BTO’s Regional representative for Perthshire, Mike Bell. Mike had the foresight to start monitoring what was an important concentration of breeding waders in Strathallan (Perthshire, Scotland) in the late 1980s. Twenty-five years after establishing repeatable methods over the study area proved an appropriate time to take stock of changes that occurred. The four most numerous species in the area were Oystercatcher, Lapwing, Curlew and Redshank, which respectively achieved densities of 12, 36, 3 and 5 pairs per km2 in 1990. All are facing serious declines across the UK. Alongside information on the breeding populations of these four waders, Mike also documented agricultural changes; from this it was possible to determine how local farming practices were likely to have influenced the waders. Over the period of 1990-2015 Oystercatchers showed the greatest proportional decline with the breeding population falling by 95%, followed by Lapwing (-88%), Redshank (-87%) and Curlew (-67%). Although the greatest declines were associated with changing land use, the declines appeared greater than could be accounted by losses of preferred habitat alone. Furthermore, breeding success was low throughout the study and probably not sufficient to maintain the population. This raises the importance of understanding the roles of source and sink populations for breeding waders in the wider countryside. Alongside this, threats from poor weather, increased disturbance (e.g. from dog walkers), and increased predator numbers could further implicate the population, although this was not studied specifically at Strathallan. Mike Bell is a long-term volunteer for the BTO and now Regional Representative for Perthshire. This 25-year (and ongoing) study was undertaken in his own time, highlighting the value of volunteers to science and conservation. It also emphasises how long-term datasets such as this can provide invaluable insights into the pressures that bird species are facing, and how we may alleviate these pressures. As most long-term studies are possible only with volunteers, the importance of their contribution is increasingly important. With support from the BTO’s recent Curlew Appeal, BTO has been trialling a range of approaches where volunteers can add to our understanding of the ecology of breeding waders, knowledge which will be vital to provide these beautiful birds with a fighting chance.

The main theme of The State of the UK’s Birds report (SUKB) 2016 is the latest Birds of Conservation Concern 4 list – BoCC4 published in 2015 - and the species whose status has changed. The increase in the Red list by 15 species is due to problems in all habitats including farmland, woodland and coasts but most notably in uplands with five new upland species moving onto the red list.One of these is Curlew. The UK supports 27% of the global population, and the long-term trend shows a 64% decline from 1970 to 2014. This, combined with the bird's global status of Near Threatened, suggests that the Curlew is one of the most pressing bird conservation priorities in the UK. “The BTO is working with others on a programme of research to understand the causes of Curlew decline and guide potential management solutions. This involves analyses of long-term data collected by thousands of volunteers, using novel tracking technology to study the needs of individual birds, and working with local enthusiasts to inform the recovery of local populations” - James Pearce-Higgins, Director of Science, BTO Upland birds Whinchat, another largely upland species monitored by the BBS shows a 53% decline during the last two decades. As an Afro-Palearctic migrant, this species is part of another group for which there is particular concern. Threats and pressures during migration and on the wintering grounds need to be considered alongside the impact of changes in upland habitats in the UK. More unexpected perhaps, is that Grey Wagtail has moved from the Amber list to the Red list. Alongside declines in Common Sandpiper and Dipper, this raises wider concerns about species associated with upland streams and rivers. The other two upland species to show marked declines are Merlin and Dotterel, the latter a montane species likely to affected negatively by climate change and grazing pressure. Scarce and rare breeding species As well as the annual update of changes in widespread breeding species based mainly on the BBS, SUKB 2016 once again includes a summary of trends in scarce and rare breeding species, drawn mainly from the annual reports of the Rare Breeding Bird Panel (RBBP) and the SCARABBS programme of periodic surveys. Of the 91 species reported on in the most recent RBBP report covering 2014, 71 were assessed by BoCC4. Eight species showed an improvement in status (including Woodlark, Bearded Tit and Chough, which joined the Green list), with conservation action to maintain suitable reed beds helping the populations of species such as Bittern recover. Five species, Pochard, Slavonian Grebe, Merlin, Dotterel and Black Redstart moved onto the Red list. The remaining 20 of the 91, not assessed by BoCC4, are those which are not considered to be a regular component of the UK’s avifauna. This may be because they breed only occasionally (eg. European Bee-eater), or indeed have never bred, but from time-to-time visiting individuals exhibit breeding behaviour (eg. Great Reed Warbler). The RBBP logs such occurrences, as it may be that they represent a precursor to future colonisation, such as the first Little Egrets that displayed to each other in the early 1990s, before first breeding in 1996 and the subsequent population explosion. The importance of volunteer data Thousands of dedicated volunteers contributed to the data used throughout most of this report. Data used to calculate UK population trends and related research. Over 2,600 volunteers participated in the Breeding Bird Survey in 2016 alone, one of many surveys highlighted in the report. This particular survey provides annual population trends for 111 species, including upland species such as Curlew, Whinchat and Grey Wagtail. At a smaller, but equally as important scale, the 258 volunteers who contribute to the Waterways Breeding Bird Survey allow monitoring on those species specific to waterways, such as Common Sandpiper and Dipper and cover almost 300 sites annually. Who produces the report SUKB is produced by a coalition of three non-governmental organisations (NGOs) – the RSPB, BTO and the WWT – and the UK Government’s statutory nature conservation agencies – Natural Resources Wales (NRW), Natural England (NE), the Department of Agriculture, Environment and Rural Affairs, Northern Ireland (DAERA), Scottish Natural Heritage (SNH) and the Joint Nature Conservation Committee (JNCC).

Terrestrial laser scanning (TLS) captures the three‐dimensional structure of habitats. Compared to traditional methods of forest mensuration, it allows quantification of structure at increased resolution, and the derivation of novel metrics with which to inform ecological studies and habitat management. Lowland woodlands in the UK have altered in structure over the last century due to increased abundance of deer and a decline in management. We compared whole‐canopy profiles between woodlands with high (>10 deer km−2) and low deer density (c. 1 deer km−2), and in stands with and without records of management interventions in the last 20 years, providing a test case for the application of TLS in habitat assessment for conservation and management. Forty closed‐canopy lowland woodlands (height range 16·5–29·4 m) were surveyed using TLS in two regions of the UK, divided into areas of high‐ and low‐deer abundance, and between plots which had been recently managed or were unmanaged. Three‐dimensional reconstructions of the woodlands were created to document the density of foliage and stem material across the entire vertical span of the canopy. There was a 68% lower density of understorey foliage (0·5–2 m above‐ground) in high‐deer woodlands, consistent in both regions. Despite this, total amounts of foliage detected across the full canopy did not differ between deer density levels. High‐deer sites were 5 m taller overall and differed in the distribution of foliage across their vertical profile. Managed woodlands, in contrast, exhibited relatively minor differences from controls, including a lower quantity of stem material at heights from 2 to 5 m, but no difference in foliage density. All main effects were replicated equally in both regions despite notable differences in stand structures between them. Synthesis and applications. Terrestrial laser scanning allows ecologists to move beyond two‐dimensional measures of vegetation structure and quantify patterns across complex, heterogeneous, three‐dimensional habitats. Our findings suggest that reduction of deer populations is likely to have a strong impact on woodland structures and aid in restoring the complex understorey habitats required by many birds, whereas management interventions as currently practiced have limited and inconsistent effects.

This report provides findings from the first year of a study that has used Movetech ‘GPS-GSM’ tracking devices to track the movements of Lesser Black-backed Gulls from a breeding colony at the Ribble and Alt Estuaries SPA and so investigate their use of the SPA and the Warton Aerodrome. The study had two main objectives: (i) to assess the flight altitudes of adult Lesser Black-backed Gulls from the breeding colony at Banks Marsh in the Ribble and Alt Estuaries SPA during the 2016 breeding season; and (ii) to assess the home ranges of adult Lesser Black-backed Gulls from this colony and their temporal and spatial overlap with the SPA and the area of potential risk of collision with aircraft.