Ian G. Henderson

Agronomic and ecological costs and benefits of set-aside in England

Abstract Around 11% of arable land in England was set-aside in the mid-1990s as part of the Common Agricultural Policy (CAP). The scheme allowed both annual and longer-term exclusion from cropping. The most widespread green cover was natural regeneration, followed by non-food crops and sown grass covers. Impacts of set-aside management on agronomy and ecology were investigated using a questionnaire for farmers and field studies of plants, invertebrates and breeding birds on up to 200 set-aside fields, half rotational and half non-rotational. More detailed studies were conducted on crop diseases, vegetation dynamics and breeding birds. Plant species diversity on set-aside was greater in the west of England than in the east, and, on non-rotational naturally-regenerated set-aside, plant communities became increasingly dominated by grassland species with age. Gradients of powdery mildew and septoria leaf blotch infection levels were observed within cereal fields adjacent to rotational set-aside. Invertebrate pest species were more frequent in crops than in neighbouring set-aside, regardless of type. All groups of birds studied were found least on winter cereals, and most were found preferentially on rotational set-aside. Set-aside (especially rotational) has provided suitable habitats for breeding birds over very large areas, and may have helped to compensate for other changes in the farmed landscape detrimental to birds, without causing major agronomic problems. It is important that any scheme replacing set-aside should be over large enough total areas so that the benefits to farmland birds across landscapes are not reduced.

Evidence for declines in populations of grassland-associated birds in marginal upland areas of Britain

Capsule We report large declines among summer populations between 1968–80 and 2000. Aim To assess changes in the status of breeding populations of birds in pastoral uplands. Methods Volunteer observers revisited 13 areas of marginal upland in Britain where Common Birds Census data were collected during 1968–80. This allowed the status of 35 bird species to be examined over about 20 years and to make a comparison between grassland-based and woodland-based species. Results For 12 species the decline in abundance was significant, particularly among passerines, such as Skylark Alauda arvensis, Wheatear Oenanthe oenanthe, Whinchat Saxicola rubetra, Yellow Wagtail Motacilla flava and Yellowhammer Emberiza citrinella, each of which declined by over 80%. Redshank Tringa totanus, Yellow Wagtail, Dipper Cinclus cinclus, Whinchat, Wheatear, Ring Ouzel Turdus torquatus and Yellowhammer were found on less than half the number of plots on which they were originally recorded. Most declining species were associated with grassland for nesting and foraging, compared to those species that increased (Wood Pigeon Columba palumbus, Pied Wagtail Motacilla alba, Carrion Crow Corvus corone, Jackdaw C. monedula and Goldfinch Carduelis carduelis) that were less specialized in their habitat requirements. Woodland or woodland edge species showed no significant change in status, suggesting that population declines among grassland species were not due to lower observer effort between recording periods. Conclusion Long-term changes to grassland ecosystems in marginal upland areas of Britain may have influenced the status of bird populations.

The response of common terns Sterna hirundo to power lines: An assessment of risk in relation to breeding commitment, age and wind speed

Abstract Common terns breed within the industrial complex at Shotton Steel Works, North Wales. Each journey between the breeding colony and the main feeding areas on the Dee estuary requires the terns to negotiate two spans of power lines. Here we investigated the risk of collision with power lines in relation to the time demands on adults, the age of birds and wind speed. Systematic observations were made of terns journeying to and from the estuary during four phases of the breeding season (courtship, incubation, nestling and juvenile). Casualty surveys of the ground beneath the power lines were also completed, and in order to quantify the potential removal rate of bird casualties by predators, bird corpses were placed underneath the power lines and recounted after two, five and 14 days. There was a greater than three-fold increase in the frequency of combined journeys made by terns from courtship to the nestling phase and this increase coincided with an increase in the proportion of adult terns which passed under or between the wires of the power lines. Terns also flew closer on average to the top earth wire during the nestling and fledging phases than during the courtship or incubation phases. Juvenile terns flew consistently closer to wires than adults with most juvenile crossings being Common terns are agile birds and suffered only low rates of direct mortality through collisions with power lines. However, the demands placed on parent birds during the breeding season caused a significant increase in their vulnerability to collision. This is a factor which has not previously been studied and has implications for a wider range of species.

Population estimates, trends and habitat associations of breeding Lapwing Vanellus vanellus, Curlew Numenius arquata and Snipe Gallinago gallinago in Northern Ireland in 1999

Capsule Declines in the breeding populations of Snipe, Lapwing and Curlew were recorded between April and June 1999 and compared with previous estimates in 1987. Aims To compare populations of non-coastal breeding waders between 1987 and 1999. Methods In 106 2 km × 2 km square tetrads, observers recorded the number of breeding pairs of waders and habitat details on 1:10 000 scale maps. Results A significant decline of c. 60% for Lapwing and Curlew, and a non-significant decline of 30% for Snipe was recorded over 12 years. Concentrations of these species were found in County Tyrone, but Counties Antrim, Down and Armagh supported few breeding pairs of any species. Very few pairs of any species were recorded on improved grassland despite its widespread availability. Conclusion A successful conservation strategy for these species must address the wider countryside and not just key sites. Intensive pastoral farming in upland and lowland areas and activities such as drainage and peat extraction will further reduce the suitability of open habitats for these wader species.

Developing and enhancing biodiversity monitoring programmes: a collaborative assessment of priorities

Summary Biodiversity is changing at unprecedented rates, and it is increasingly important that these changes are quantified through monitoring programmes. Previous recommendations for developing or enhancing these programmes focus either on the end goals, that is the intended use of the data, or on how these goals are achieved, for example through volunteer involvement in citizen science, but not both. These recommendations are rarely prioritized. We used a collaborative approach, involving 52 experts in biodiversity monitoring in the UK, to develop a list of attributes of relevance to any biodiversity monitoring programme and to order these attributes by their priority. We also ranked the attributes according to their importance in monitoring biodiversity in the UK. Experts involved included data users, funders, programme organizers and participants in data collection. They covered expertise in a wide range of taxa. We developed a final list of 25 attributes of biodiversity monitoring schemes, ordered from the most elemental (those essential for monitoring schemes; e.g. articulate the objectives and gain sufficient participants) to the most aspirational (e.g. electronic data capture in the field, reporting change annually). This ordered list is a practical framework which can be used to support the development of monitoring programmes. Peoples ranking of attributes revealed a difference between those who considered attributes with benefits to end users to be most important (e.g. people from governmental organizations) and those who considered attributes with greatest benefit to participants to be most important (e.g. people involved with volunteer biological recording schemes). This reveals a distinction between focussing on aims and the pragmatism in achieving those aims. Synthesis and applications. The ordered list of attributes developed in this study will assist in prioritizing resources to develop biodiversity monitoring programmes (including citizen science). The potential conflict between end users of data and participants in data collection that we discovered should be addressed by involving the diversity of stakeholders at all stages of programme development. This will maximize the chance of successfully achieving the goals of biodiversity monitoring programmes.

The status of breeding Woodlarks Lullula arborea in Britain in 2006

Capsule There have been marked increases (88%) in the breeding population and breeding range (46%) of Woodlarks in Britain between 1997 and 2006. Aims To provide an accurate assessment of the population and distribution of Woodlarks in Britain and how these have changed since a survey conducted in 1997. Methods Survey coverage included ‘core’ 1 km squares (known occupancy in 1997) and a stratified random sample, based on suitable habitat and soil type. Results A population estimate of 3064 territories was obtained, giving an increase of 88% since 1997, while the range of occupied 10 km squares had increased by 46%. The majority of territories were associated with two main habitat types; heathland (66.7%) and forestry plantation (32.4%), and farmland in the southwest (13.4%). Sandy soils held the majority of territories (80.3%). Conclusion In the UK, the Woodlark is a species of high to moderate conservation concern subject to a national Biodiversity Action Plan (BAP). This survey demonstrated that the population has increased to meet the BAP targets set in 1996 for population size and range expansions in England, and is on schedule to meet targets in Wales. The species has responded to conservation restoration projects and is highly dependent on forest management.

Agricultural Management and Climatic Change Are the Major Drivers of Biodiversity Change in the UK.

Action to reduce anthropogenic impact on the environment and species within it will be most effective when targeted towards activities that have the greatest impact on biodiversity. To do this effectively we need to better understand the relative importance of different activities and how they drive changes in species’ populations. Here, we present a novel, flexible framework that reviews evidence for the relative importance of these drivers of change and uses it to explain recent alterations in species’ populations. We review drivers of change across four hundred species sampled from a broad range of taxonomic groups in the UK. We found that species’ population change (~1970–2012) has been most strongly impacted by intensive management of agricultural land and by climatic change. The impact of the former was primarily deleterious, whereas the impact of climatic change to date has been more mixed. Findings were similar across the three major taxonomic groups assessed (insects, vascular plants and vertebrates). In general, the way a habitat was managed had a greater impact than changes in its extent, which accords with the relatively small changes in the areas occupied by different habitats during our study period, compared to substantial changes in habitat management. Of the drivers classified as conservation measures, low-intensity management of agricultural land and habitat creation had the greatest impact. Our framework could be used to assess the relative importance of drivers at a range of scales to better inform our policy and management decisions. Furthermore, by scoring the quality of evidence, this framework helps us identify research gaps and needs.

Dominance, food acquisition and reproductive success in a monogamous passerine: the Jackdaw Corvus monedula

By manipulating the density and area of a food supply of grain offered to wild Jackdaws we showed that individuals in flocks varied in their ability to acquire food through direct physical competition, and that the relative pay-offs to individual competitors varied according to the distribution of the resource. There was a disproportionate ability of some individuals to occupy preferred flock positions or feeding sites and higher ranking males had greater access to clumped food. Rank was positively correlated with the more efficient provisioning of offspring and the raising of larger annual broods, but reproductive success and social status were also strongly dependent on age. Our results provided evidence that attributes of dominance (e.g. fighting ability) are valuable for maintaining access to increasingly restricted food supplies. Since the rank of an individual is explained at least in part by age we discuss the consequences of this for the durability of the pair-bond and life-time reproductive success.

National and regional patterns of habitat association with foraging Barn Swallows Hirundo rustica in the UK

Capsule Barn Swallows showed a consistent association with cattle across the UK, but certain landscape features, particularly mixed field types and tall trees, were also important. Aim To provide nationally representative data on habitat selection in foraging Barn Swallows. Method Observers carried out four timed point counts within an allocated 2-km square(s). Point counts were at least 500 m apart and considered as independent sample points. Each point count covered 100 m radius and was visited twice during the summer. An index of foraging activity was derived from the number of foraging passes made by Barn Swallows within ten minutes. The maximum count of Swallows present was also recorded. Habitat data included the presence or absence of landscape features and buildings and the proportion of area covered by particular crop and boundary types within the 100 m count radius. Results Cattle were the single most important and most consistent variable associated with foraging Barn Swallows, in every UK region. Horses were also important in the southeast. Grassland was only important if livestock were present. Foraging pass rates were higher where count circles contained a mixture of grass and arable fields rather than just one or the other. There was a general positive relationship between foraging pass rates and the presence of tall trees in boundaries, and this was significant in the arable eastern region of the UK, where their relative importance of concentrating prey may be more acute. Conclusion Historical changes in the distribution and availability of habitat features associated with foraging Barn Swallows are consistent with regional differences in population change for this species in the UK. These patterns of association are discussed in terms of changes in land use, the widespread loss of mixed farming and simplifications to landscape complexity.

Status and distribution of European Nightjars Caprimulgus europaeus in the UK in 2004

Capsule The population of Nightjars in the UK increased by over 36% between 1992 and 2004. Aims To determine the population size and distribution of Nightjars in the UK and examine associations with forestry and heathland habitat features. Methods A volunteer survey was supported by professional cover in remote parts of Wales, and areas of Dorset and lowland Scotland. Two visits to allocated 1-km squares were made between late May and mid-July. Each surveyor recorded the locations of calling males onto maps and the occurrence of habitat categories within 50 m of each Nightjar registration. Results Observers surveyed 3264 1-km squares in 2004 and, on average, 78% of the target habitat (90% in southern England). The total number of males counted was 4131 (range 3850–4414), adjusted to 4606 (95% CL ± 913) to account for unsurveyed habitat. The adjusted total represented a 36% increase in 12 years. Nightjars were recorded in 275 10-km squares in 2004, a 2.6% increase since 1992. However, there was evidence of population decline and range contractions in northwest Britain, including north Wales, northwest England and in Scotland. In 2004, 57% of Nightjars were associated with forest plantations (similar to 1992) and 59% with heathland (slightly higher than in 1992). Conclusion National objectives for Nightjar conservation (UK Biodiversity Action Plan: UKBAP) were reached in respect of population size and stability, but the target for a 5% range increase by 2003 was not met. The continued increase in the national population is probably attributable to habitat protection, management and restoration of heathlands, and the continued availability of clear-fell/young plantations in conifer forests. Management and/or protection/restoration/re-creation of these key habitats remains critical for the long-term objectives of UKBAP. The issue of providing foraging habitats, perhaps via agri-environment schemes, is also raised.