Prior to this study, most Tawny Owl population data were collected during daylight surveys for other species, or specialist, labour-intensive night-time surveys during the breeding season. The BTO Tawny Owl Calling Survey, however, harnessed the time and skill of thousands of volunteers to shed light on the impact of urbanisation on Tawny Owl populations, and used the data collected to develop the best methods for surveying these nocturnal raptors in the future.

International collaborative research involving BTO has used data collected 30 years apart, during the two European Breeding Bird Altases, to examine range shifts in wetland birds.

Researchers from BTO and the scientific department of Belarusian Chernobyl analysed 22 years of raptor population data from the Chernobyl Exclusion Zone (CEZ) and identified the impact of reduced human activity on some of Europe’s rarest birds of prey. Their findings demonstrate the power of rewilding for supporting biodiversity, including the conservation of vulnerable species. Over 2,000 km² of Belarus previously given over to intensive agriculture and dense settlements was affected by the 1986 reactor meltdown at the Chernobyl Nuclear Plant in Ukraine. Since then, this area has experienced little to no human disturbance, leading to decades of ‘passive rewilding’ where nature has been left to its own devices. This study explores the effects of this passive rewilding on the bird of prey community inhabiting the area; birds of prey sit at the top of the food chain and are thus excellent indicators of ecosystem health. The authors used a long-term dataset developed from periodic surveys of breeding birds of prey within a 147 km² study plot towards the edge of the Belarusian Chernobyl Exclusion Zone (CEZ). The researchers also used satellite imagery to analyse changes in land cover throughout this period, finding significant shifts in the area occupied by different types of habitat over time. Former agricultural land either became overgrown or rewetted, and the increase in waterlogged areas saw wetland specialists increase in abundance. Two wetland specialist that had been locally extinct in the area prior to the accident – Greater Spotted Eagle and White-tailed Eagle – both returned and increased in number. The study also followed the populations of 12 other raptor species from 1998 to 2019. Different species assemblages – the abundance and type of species present in an area – are associated with different habitats. Analysing the changes in abundance showed a decline in generalist predators, such as Montagu’s Harrier and Buzzard, which hunt over open fields and farmland and eat a variety of prey species, and an increase in specialists such as Greater Spotted Eagles and Hobby. Because some of the specialists are dependent on other important conservation species for food, for example Corncrake and Great Snipe, this change indicates a positive impact of rewilding on the ecosystem as a whole, not just the raptor populations, and shows rewilding’s potential value as a strategy to tackle biodiversity loss.

Mountain and upland regions harbour a high proportion of global biodiversity and have a high rate of endemism, but few assessments of environmental change have been conducted in these areas in compared with more accessible biomes.

New research led by BTO scientists has examined the effect of food supplies on Oystercatchers in Wales, showing how populations are affected by the availability of prey species, and underlining the importance of alternative foraging areas close by. Oystercatcher numbers are declining in the UK, in line with the trends for wader species globally, and with ever greater anthropogenic changes to wader habitats, it is vital we understand the processes driving population change if we are to take effective conservation action. This study used data from the Wetland Bird Survey (WeBS) and ringing to assess the effect of Cockle availability on wintering Osytercatcher numbers in south Wales. Cockles are an important prey species for Oystercatchers and other wader species, leading to competition for this food resource with humans, who commercially fish Cockles and other shellfish. Burry Inlet in south Wales formerly had a highly productive Cockle fishery, but in 2004 numbers crashed, with larger, older Cockles especially affected. Smaller Cockles have since gradually become re-established, but larger Cockle stocks have yet to recover. Burry Inlet is also a Special Protection Area for birds. Following the 2004 crash, the number of Oystercatchers recorded during WeBS counts on Burry Inlet fell, but there was an increase in birds counted in the neighbouring Three Rivers Estuary, part of the Carmarthen Bay Special Area of Conservation, suggesting some Oystercatchers simply moved from one site to the other. Data from ringing also showed an apparent reduction in survival of Oystercatchers using Burry Inlet in years of low Cockle biomass. The fact that Oystercatchers were able to move to a nearby site, where Cockle harvesting had been capped due to regulations associated with the area’s protected status, shows the importance of having resilient networks of protected areas. Such networks can buffer fluctuations in the suitability of individual sites to particular species. The study also underlines the importance of long-term monitoring in accurately understanding the effects of incidents such as the Burry Inlet Cockle crash, allowing for optimal management of both protected area networks and fishery practices.