Britain and Ireland support globally-important numbers of breeding seabirds, but these populations are under pressure from a suite of threats, including marine pollution, habitat loss, overfishing and highly pathogenic avian influenza. Climate change introduces additional threats, the magnitude of which is uncertain in the future, making it difficult to plan how to apportion conservation efforts between seabird species. Predicting how species’ numbers could change under different climate change scenarios helps clarify their future vulnerability to extinction, and thus assists in conservation planning.

Ongoing declines have been reported for many of our wader species, and there is an urgent need to both understand the reasons for these declines and assess the effectiveness of any associated conservation action. Intertidal habitats are often well-used by waders outside the breeding season, but some species also make use of other adjacent habitats during this period, including agricultural fields. Understanding the importance of these non-tidal habitats for waders is crucial, especially as such land is rarely included within the protected areas designated for these species. This study investigates the use of non-tidal habitats bordering The Wash – an estuary in eastern England – by Curlew and Bar-tailed Godwit, species which are designated as ‘Near Threatened’ by the IUCN. Information on the winter-feeding distribution of the two species was collated from resightings of individually colour-marked birds, initially caught and ringed at sites around The Wash by the Wash Wader Research Group. The sex of individual birds was determined from measurements taken in the field, and this provided an opportunity to determine if males and females differed in their use of the available habitats. The resightings revealed that Bar-tailed Godwits were only seen on intertidal habitats and none were observed feeding inland. In contrast, colour-marked Curlews were regularly observed feeding on agricultural fields, the colour-marks revealing that the majority of individuals were feeding on both fields and mud flats. Importantly, those Curlews seen feeding in fields were significantly more likely to be male and those on the estuary more likely to be female. Although there is a small degree of overlap, female Curlews have longer bills than males. The difference in habitat use evident in the resighting data probably reflects the fact that the longer-billed females can access more intertidal worms and are more efficient feeders when probing. Shorter-billed individuals may be better suited to feeding in the denser substrate typical of agricultural fields, and they may also struggle to find sufficient prey when using intertidal areas. That inland fields are used by increasing numbers of Curlews, particularly males, through the winter months has implications for existing conservation approaches. The Wash is protected by various national and international designations, but these relate primarily to the intertidal habitats; the inland fields are not protected and are subject to pressure on land for development. Should these inland feeding sites be lost this is likely to affect males (particularly those with the shortest bills) disproportionately, which may have implications for the wider Curlew population. The study’s findings suggest that consideration should be given to extending the area around The Wash receiving protection.

It is important for birds to maintain their plumage in good condition, something that is facilitated by the periodic moulting of their feathers. However, moulting feathers is energetically costly and can also compromise an individual’s ability to forage and avoid predators. Because of this, the timing of feather moult needs to be balanced against the demands imposed by other key events, such as breeding and migration.

Habitat loss and climate change are two major threats to global biodiversity. How these two threats interact to drive biodiversity changes is less well understood. In this study, the authors examined changes in bird, butterfly, moth and plant distributions across the UK over the past 75 years to investigate how species respond to these combined threats.

In an effort to cut carbon emissions, many countries (including the UK) are constructing ever more offshore wind farms. Seabirds are at risk of colliding with the blades of offshore wind turbines, posing the potential for injury or death. However, the extent of this risk depends on several factors including how high the seabirds fly in relation to the area swept by turbine blades, the seabirds’ flight speeds, and any avoidance behaviour they undertake in response to either individual turbines or entire wind farms. Accurate understanding of these behavioural aspects of seabirds is important when assessing the potential population impact an offshore wind farm will have through so-called Collision Risk Models (CRMs). As previous BTO research has shown, bird-borne tracking devices are essential for shedding light on seabird flight behaviour. Different methods for gathering flight height information within tracking devices can influence the altitudes they produce, with implications for the collision estimates ultimately produced. This study compared the flight height altitudes produced from GPS and barometric altimeter data from tagged Lesser Black-backed Gulls to investigate this matter. Novel methods for calibrating GPS and altimeters were trialled to reduce error within the altitudes calculated by these methods as much as possible. The data were collected by attaching tracking devices to adult Lesser Black-backed Gulls captured while they were incubating their eggs at two breeding colonies (the Isle of May in Scotland and Havergate Island in England) in 2019 and 2020. Tags contained both GPS, which estimates a bird’s position using a network of satellites, and altimeters, which use air pressure measurements to estimate flight height. These two systems enabled flight heights obtained from either method to be compared. The results showed that altimeter data, when combined across years and colonies, produced higher flight heights than GPS data, and that this difference was more marked at higher sampling frequencies (e.g. one data point every 10 seconds) than at lower ones (e.g. one data point every five minutes). This in turn led to a greater number of collisions being predicted by CRMs for altimeter data than for GPS data. However, when GPS-altimeter data was split by sampling rate, year, and colony, flight heights from altimeters were not consistently higher, indicating local environmental conditions play a role influencing the accuracy of altitudes recorded. Tracking devices can provide information on flight height across a range of behaviours and environmental conditions. Improvement of calibration steps to account for the influence of the environment on tracking devices will help improve the accuracy of flight height information collected in future. This will increase confidence in the use of tracking devices in future assessments of collision risk and help to better predict mortality associated with wind farms. Forming a better understanding of the impacts of wind farms on seabirds will help ensure their appropriate development in future throughout the North Atlantic.