Density-dependent competition for food influences the foraging behaviour and demography of colonial animals, but how this influence varies across a species’ latitudinal range is poorly understood. Here we used satellite tracking from 21 Northern Gannet Morus bassanus colonies (39% of colonies worldwide, supporting 73% of the global population) during chick-rearing to test how foraging trip characteristics (distance and duration) covary with colony size (138–60 953 breeding pairs) and latitude across 89% of their latitudinal range (46.81–71.23° N). Tracking data for 1118 individuals showed that foraging trip duration and maximum distance both increased with square-root colony size. Foraging effort also varied between years for the same colony, consistent with a link to environmental variability. Trip duration and maximum distance also decreased with latitude, after controlling for colony size. Our results are consistent with density-dependent reduction in prey availability influencing colony size and reveal reduced competition at the poleward range margin. This provides a mechanism for rapid population growth at northern colonies and, therefore, a poleward shift in response to environmental change. Further work is required to understand when and how colonial animals deplete nearby prey, along with the positive and negative effects of social foraging behaviour.

Offshore wind farms (OWFs) are a key part of efforts to mitigate the impacts of climate change. However, they have the potential to negatively impact seabird species through collisions with turbine blades, displacement from preferred foraging habitat and the perception of wind farms as a barrier to migrating or foraging birds. Whilst the data available to model these impacts are increasing, many data gaps remain, particularly in relation to the impacts of barrier effects. We analyse the movements of Sandwich terns in relation to an offshore wind farm cluster using data collected as part of a multi-year GPS tracking study. Over the course of the study, two additional wind farms were built within the home range of the breeding colony. The construction of these wind farms coincided with a change in the foraging and commuting areas used by breeding terns. Whilst birds entered OWFs when foraging, they appeared to avoid them when commuting, driving an apparent ‘funnelling’ effect to important feeding locations. We discuss if this could be driven by changes to the prey base, subsequent displacement and potentially altered routes reflecting new favourable airflow patterns following OWF construction. Our results suggest that behavioural responses of birds to OWFs may be the result of a complex series of ecological and environmental interactions, as opposed to simplistic assumptions around the perception of the OWF as a barrier to movement.

During 2021 and 2022 High Pathogenicity Avian Influenza (HPAI) killed thousands of wild birds across Europe and North America, suggesting a change in infection dynamics and a shift to new hosts, including seabirds. Northern Gannets Morus bassanus appeared to be especially severely impacted, but a detailed account of the data available is required to help understand how the HPAI virus (HPAIV) spread across the meta-population, and the ensuing demographic consequences. Accordingly, we analyse information on confirmed and suspected HPAIV outbreaks across most North Atlantic Gannet colonies and, for the largest colony (Bass Rock, UK), provide impacts on population size, breeding success, and preliminary results on apparent adult survival and serology. Unusually high numbers of dead Gannets were first noted at colonies in Iceland during April 2022. Outbreaks in May occurred in many Scottish colonies, followed by colonies in Canada, Germany and Norway. By the end of June, outbreaks had occurred in colonies in Canada and the English Channel. Outbreaks in 12 UK and Ireland colonies appeared to follow a clockwise pattern with the last infected colonies recorded in late August/September. Unusually high mortality was recorded at 40 colonies (75% of global total colonies). Dead birds testing positive for HPAIV H5N1 were associated with 58% of these colonies. At Bass Rock, the number of occupied nest-sites decreased by at least 71%, breeding success declined by c. 66% compared with the long-term UK mean and the resighting of marked individuals suggested that apparent adult survival between 2021 and 2022 could have been substantially lower than the preceding 10-year average. Serological investigation detected antibodies specific to H5 in apparently healthy birds, indicating that some Gannets recover from HPAIV infection. Further, most of these recovered birds had black irises, suggestive of a phenotypic indicator of previous infection. Untangling the impacts of HPAIV infection from other challenges faced by seabirds is key to establishing effective conservation strategies for threatened seabird populations as the likelihood of further epizootics increases, due to increasing habitat loss and the industrialization of poultry production.

Transitioning to renewable energy is crucial for meeting net-zero targets to tackle the climate crisis. Although wind and solar are the main generation methods being pursued, they risk exacerbating future land-use challenges. Here, we explore the UK’s land capacity to accommodate two levels of increased future onshore wind and solar energy capacity. We quantify the impact on breeding bird habitat, food production, and net greenhouse gas flux in the presence and absence of a range of nature-based climate change mitigation measures. We find that even the highest onshore renewable energy ambitions require only a small fraction of the suitable land area, with little cost to food production, greenhouse gas sequestration, or breeding birds, even under pessimistic modeling assumptions. Therefore, the UK could boost onshore renewables without contributing substantially to future land competition, especially if potential synergies between multiple land uses, such as cropping and solar, are realized.

With coastal wader populations exhibiting long-term declines globally, understanding how they respond to changes in their preferred prey is important for future predictions, especially given the potential for warming seas to affect invertebrate populations. The cockle Cerastoderma edule population in the Burry Inlet Special Protection Area (SPA) in south Wales, UK, declined from 1997-2004 before an abrupt 'crash' in stocks between 2004 and 2010. While there has been some recovery since, stocks of larger cockles are still very low. Using survey data from the UK Wetland Bird Survey and analyses of apparent survival and biometrics from ringing, we investigated how the Burry Inlet SPA's wintering Eurasian oystercatcher Haematopus ostralegus population responded to this crash. Our analysis showed that both body condition and apparent survival of wintering adult oystercatchers were reduced in the years following the cockle crash but both recovered. The number of birds using the Burry Inlet SPA decreased through the course of the cockle stock decline whilst numbers of birds in the adjacent Carmarthen Bay increased, indicating the importance of adjacent sites for buffering the effects of such changes, i.e. protected secondary habitats can be a vital component of a resilient site network. Our findings are useful in understanding how a predator copes with a serious decline in its preferred food stocks. This study has wide applicability in planning the management of coastal wetlands and shellfisheries as well as the design of resilient protected area networks in the light of environmental change.

Migratory species face geographically dispersed pressures over the course of their annual cycles. Designing effective conservation strategies for these species requires a detailed understanding of how these different pressures affect demographic rates throughout the annual cycle. As a long-lived species, population trends in the rapidly declining Eurasian curlew Numenius arquata are likely to be highly sensitive to impacts on adult survival. We combine data from multiple sources to analyse survival rates of overlapping populations that breed and/or winter in the United Kingdom. Our analyses demonstrate that curlew survival rates are reduced by cold weather and at high density; however, overall survival rates are high and have increased in recent years. Current population declines are, therefore, likely to be driven by low productivity. As such, efforts to stabilise and reverse declines should focus on increasing breeding success from current estimated levels of 0.25 chicks nest−1 to 0.43 chicks nest−1. In addition to increasing productivity, effective conservation strategies will need to maintain high levels of survival, which requires an improved understanding of population connectivity and demographic variation throughout the annual cycle.

Biodiversity is valuable to society, including through its contribution to cultural benefits: "the non-material benefits people obtain from biodiversity and ecosystem services through spiritual enrichment, cognitive development, reflection, recreation, and aesthetic experiences". Biodiversity encompasses numerous measures, but the distinct values of these measures have been little studied. We conducted a discrete choice experiment to elicit respondents' (n = 3000) willingness to pay for increases in four measures of bird diversity in UK coastal ecosystems: number of bird species (species richness), number of individual birds (abundance), probability of seeing rare or unusual bird species, and probability of seeing large flocks of birds (wildlife spectacles). Respondents had a positive willingness to pay (through one-time voluntary donations) for increases in all four measures (mean 3 pound to 5 pound per household). However, using latent class analysis we found considerable heterogeneity of preferences, identifying four classes of respondents with strikingly different levels of marginal willingness to pay for the four measures. Income, age, environmental activity, visits to environmental settings, and gender were important determinants of class membership. While focussing on birds, our results demonstrate the importance of a multidimensional conceptualisation of biodiversity in broader ecosystem management, rather than focussing on a single aspect such as species richness or abundance. Our findings also highlight the implications of heterogeneous public preferences for biodiversity for conservationists, planners, shoreline managers and developers. These need to be considered in the development of new frameworks for ecosystem services, and when planning and funding conservation actions so that the cultural benefits will accrue across a range of social groups.

Capsule Black Grouse declines across Scotland were greatest on less heterogeneous moorland, at low to intermediate altitudes and, more weakly, around post-thicket woodland.Aims To examine correlates of change in abundance of Black Grouse across Scotland.Methods Changes in abundance within 5-km squares between national surveys in 1995/96 and 2005 were modelled in relation to measures of habitat cover and woodland age derived from satellite imagery.Results Populations across Scotland were most stable where unenclosed moorland comprised rough grassland, intermediate heather cover and at higher altitude. Declines tended to be greatest in squares which had transitioned from pre-thicket to closed-canopy woodland.Conclusion Moorland will be most beneficial where it is heterogeneous in composition, and the role of woodland maturation in driving regional declines has support, albeit more weakly, at a national scale.

Summary Wind energy generation is increasing globally, and associated environmental impacts must be considered. The risk of seabirds colliding with offshore wind turbines is influenced by flight height, and flight height data usually come from observers on boats, making estimates in daylight in fine weather. GPS tracking provides an alternative and generates flight height information in a range of conditions, but the raw data have associated error. Here, we present a novel analytical solution for accommodating GPS error. We use Bayesian state‐space models to describe the flight height distributions and the error in altitude measured by GPS for lesser black‐backed gulls and great skuas, tracked throughout the breeding season. We also examine how location and light levels influence flight height. Lesser black‐backed gulls flew lower by night than by day, indicating that this species would be less likely to encounter turbine blades at night, when birds’ ability to detect and avoid them might be reduced. Gulls flew highest over land and lowest near the coast. For great skuas, no significant relationships were found between flight height, time of day and location. We consider four ‘collision risk windows’, corresponding to the airspace swept by rotor blades for different offshore wind turbine designs. We found the highest proportion of birds at risk for a 22–250 m turbine (up to 9% for great skuas and 34% for lesser black‐backed gulls) and the lowest for a 30–258 m turbine. Our results suggest lesser black‐backed gulls are at greater risk of collision than great skuas, especially by day. Synthesis and applications. Our novel modelling approach is an effective way of resolving the error associated with GPS tracking data. We demonstrate its use on GPS measurements of altitude, generating important information on how breeding seabirds use their environment. This approach and the associated data also provide information to improve avian collision risk assessments for offshore wind farms. Our modelling approach could be applied to other GPS data sets to help manage the ecological needs of seabirds and other species at a time when the pressures on the marine environment are growing.

Growing concerns about climate change and energy security have fuelled a rapid increase in the development of offshore and marine renewable energy installations (OMREIs). The potential ecological consequences of increased use of these devices emphasises the need for high quality environmental impact assessment (EIA). We demonstrate that these processes are hampered severely, primarily because legislation does not ensure that the significance of impacts and cumulative effects are properly assessed. We highlight why the regulatory framework leads to conceptual ambiguities and propose changes which, for the most part, do not require major adjustments to standard practice. We emphasise the importance of determining the degree of confidence in impacts to permit the likelihood as well as magnitude of impacts to be quantified and propose ways in which assessment of population-level impacts could be incorporated into the EIA process. Overall, however, we argue that, instead of trying to ascertain which particular developments are responsible for tipping an already heavily degraded marine environment into an undesirable state, emphasis should be placed on better strategic assessment.

Making use of an extensive network of volunteer birdwatchers, this study illustrates how a large-scale monitoring scheme originally designed for common breeding birds can be adapted to also provide robust monitoring data for medium-to large-sized, easily detectable terrestrial mammals. Compared with bird monitoring, the monitoring of common and widespread terrestrial mammals is rarely carried out using a well-designed sampling design and is largely restricted to sites selected by the observer or biased towards particular habitats of interest, making it difficult to know whether trends are representative of the populations of interest. In response to the scarcity of reliable mammal monitoring data in the UK, the principal national bird monitoring scheme, the Breeding Bird Survey (BBS), was expanded to collect information on mammals. The focus was on larger, easily detectable species, although observers have the opportunity to record any mammal species. Here, we present population trends at national and regional scales for nine species of common mammal over the first 18 years of BBS mammal monitoring and examine these in relation to our current knowledge on these species. We further discuss the potential of these data for addressing important questions of conservation and management concern which may be difficult to explore with existing data.

Summary The number of offshore wind farms is rapidly increasing as they are a critical part of many countries' renewable energy strategies. Quantifying the likely impacts of these developments on wildlife is a fundamental part of the impact assessments required in many regions before permission for developments is granted. A key concern related to wind turbines is the risk of birds colliding with turbine blades. We present a novel method to generate species‐specific flight height distributions which can be used to improve the assessment of collision risk by better reflecting the proportion of in‐flight populations at risk of collision. Data describing the flight heights of birds from surveys of 32 potential offshore wind farm development sites were combined to estimate continuous distributions for 25 marine bird species. Observations of flying birds assigned to discrete height categories were treated as observations from independent multinomial distributions with a shared underlying continuous distribution. This analysis enables calculation of the uncertainty around the estimates of the proportion of the in‐flight population at risk and consideration of different turbine designs. The mean r2 for model fit across species was 0·85, and for seven of the species, good independent model validation (80% of independent observations within 95% confidence intervals) provides some confidence for use of the results at alternative sites. All species exhibited positively skewed flight height distributions. These results demonstrate that under the conditions in which the data were collected, raising hub height and using fewer, larger turbines are effective measures for reducing collision risk. Synthesis and applications. The methods presented here for modelling continuous flight height distributions provide measures of uncertainty and enable comparison of collision risk between different turbine designs. This approach will improve the accuracy of impact assessments and provide estimates of uncertainty, allowing better evidence to inform decision‐making.

This is the 73rd annual report of the British Trust for Ornithology's Ringing Scheme, covering data received and work carried out in 2009. Much of the research carried out during the year looked at ways to improve the analysis of ringing data to understand population change. This included producing survival rates from the Constant Effort Sites (CES) scheme for the first time and further developing methods of analysing our demographic data sets in an integrated manner. Research was also undertaken on the biometric data to investigate how individual condition responds to long‐term environmental change. CES data suggested that the low productivity in 2007 and 2008, combined with one of the coldest winters since 1995/96 for residents, contributed to reduced adult numbers in 2009 in many species. There were significant decreases in Wren Troglodytes troglodytes, Sedge Warbler Acrocephalus schoenobaenus, Reed Warbler A. scirpaceus, Blackcap Sylvia atricapilla, Lesser Whitethroat S. curruca, Willow Warbler Phylloscopus trochilus, Long‐tailed Tit Aegithalos caudatus, Blue Tit Cyanistes caeruleus, Great Tit Parus major, Treecreeper Certhia familiaris, Chaffinch Fringilla coelebs, Greenfinch Carduelis chloris and Reed Bunting Emberiza schoeniclus. However, a good breeding season, for both residents and migrants, resulted in significantly higher productivity for 15 species, but significantly lower for Willow Tit Poecile montana, compared to the long‐term mean (1983–2007). Data for 104 Retrapping Adults for Survival studies were submitted, covering 39 species, three quarters of which are Birds of Conservation Concern. The total number of birds ringed (935,867) was the highest ever recorded, and was over 10% higher than the mean of the previous five years. However, the total number of pulli ringed in 2009 (179,712) was only 5% higher than the preceding five‐year mean, while that of fully grown birds (756,155) was over 13% higher. The recovery total (14,643) was also high. However, this is partly due to changes in the way that records of colour‐ringed and other specially marked birds are stored. The number of recoveries of foreign‐ringed birds (1,314) was higher than the mean of the preceding five years, although this figure is influenced by varying response times of different ringing schemes. Recovery details for 250 individual birds are given in the final section of the report. They include movements that confirm suspected or known migration patterns, unexpected movements and longevity records.

1. We examined the influence of local weather conditions on reproductive success, timing of breeding and survival in a population of a multi-brooded ground nesting passerine (woodlark Lullula arborea) over 35 years. 2. Woodlarks laid larger clutches when rainfall was low and temperature high during the egg-laying and pre-laying period. Nest success increased with higher temperatures during the nesting period. In successful nests, the number of chicks fledged per egg laid was greater when weather was drier during the brood stage. 3. Although woodlarks bred earlier in years with warmer early spring temperatures, with the onset of breeding varying by 25 days, there was no significant advance in the onset of breeding over the 35 years of study, due to considerable inter-annual variability, and no overall trend, in weather. 4. Simulation modelling of annual reproductive output demonstrated that earlier breeding could increase productivity by 23.5% in the warmest compared to the coldest year, due to birds having more nesting attempts. Other effects of weather on productivity affected breeding output to a lesser extent. 5. Effects of weather on productivity were minor compared to an increased rate of nest predation through the period of study, which reduced productivity by 49.8% by 2004 compared to 1971. 6. Turning points analysis identified three distinct demographic periods: from 1971 to 1988 the population grew slowly, during 1988-1999 the population grew rapidly, but after 1999 the population declined. Increased population growth after 1988 was associated with higher first-year survival rates (estimated using a population model). Population decline after 1999 was caused by a combination of reduced productivity (resulting from increased nest failure rates attributed to predation) and lower first-year survival rates, that appear unrelated to winter temperature. 7. Climate change (long-term changes in weather) did not explain the marked changes observed in the population trajectory over 35 years. We suggest that understanding effects of both climate and habitat change on populations is essential in predictive population modelling.

The Nightjar Caprimulgus europaeus and Woodlark Lullula arborea are identified as species of conservation concern at both a UK and a European level on account of historical declines in their population sizes and ranges. The UK populations of both species have increased significantly in recent decades and this paper reviews the extent, nature and causes of these population changes, based on evidence from national surveys and autecological studies. It also considers the future prospects of both species in the face of likely changes to their preferred habitats in Britain. Nightjar numbers have increased greatly since the national survey in 1981, when the British population was estimated at only 2100 churring males, with an estimated 3400 in 1992 and 4606 (± 913) in 2004. Population recovery has been closely associated with their colonization of clear‐fell areas in planted forests. Over 57% of the calling (‘churring’) males recorded were in planted forests in 2004. Woodlark numbers have also made a substantial recovery from a low level of just 250 territories in 1986 to 1426–1552 territories in 1997. Over 85% of the Woodlark territories recorded in 1997 were on heathland or in planted forests. Despite these increases, both species continue to occupy only part of their much more extensive former breeding ranges. The recovery of these species has coincided with the availability of suitable open ground habitat resulting from the felling of forests planted in the late 1920s and 1930s, often on former heathland habitats, the clearance and restocking of areas damaged by storms in October 1987 and January 1990 and the restoration of heathland habitats. Forests and heathlands support the majority of the breeding populations of Nightjars and Woodlarks, although there are regional variations in their relative importance. The prospects for further recovery may be limited due to a reduction of open ground habitat following restocking of planted forests, including those damaged in the storms of 1987 and 1990, the effects of recreational disturbance and, at least locally, poor Woodlark breeding productivity due to predation.

Capsule Set-aside schemes have allowed breeding Woodlarks to colonize farmland, but heathland and forestry habitats remain the stronghold.Aims To determine which habitats provide the best conditions for breeding Woodlarks and whether a buffer effect is operating, with density increasing faster in the poorer quality habitat as the population grows.Methods Habitat colonization was examined and breeding success compared among heathland, clear-felled and young conifer plantations, and farmland set-aside.Results Woodlarks on heathland and forestry habitats had similar clutch sizes and nesting success, but clutch sizes may be lower on farmland. Heathland was recolonized when population density was low in forest habitats, while farmland was colonized when density was increasing, and areas close to forest were preferentially occupied. Woodlarks breeding on farmland preferred set aside stubbles to other field types.Conclusion Forestry and heathland habitats are similar in quality for breeding Woodlarks, with no evidence for a buffer effect. Farmland set-aside may be suboptimal but the area available is much greater than the area of forest or heathland, and could therefore make a significant contribution to the conservation of the Woodlark population. However, set-aside should not be seen as an alternative to the conservation of forest and heathland.