Showing papers by "Royal Society for the Protection of Birds published in 2004"

Extinction risk from climate change

Abstract: Climate change over the past approximately 30 years has produced numerous shifts in the distributions and abundances of species and has been implicated in one species-level extinction. Using projections of species' distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth's terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power-law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15-37% of species in our sample of regions and taxa will be 'committed to extinction'. When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction ( approximately 18%) than mid-range ( approximately 24%) and maximum-change ( approximately 35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse gas emissions and strategies for carbon sequestration.

Biodiversity Impacts of Some Agricultural Commodity Production Systems

Abstract: Despite centuries of urbanization and industrialization, around half of the world’s people still live as subsistence or small-scale farmers. The production of agricultural export commodities represents a major source of foreign income for many developing countries, and commodities such as coffee and cocoa rank second in importance only to oil in legal international trade. Such crops are inevitably produced on land formerly covered with natural habitats, and their production usually involves the loss of some or most of the biodiversity formerly present. Around 15 million ha of the Earth’s primary forest are lost each year, most of it in the tropics. Of this, approximately 60% is lost to slash-and-burn agriculture, the rest to logging, other forms of agriculture, and fire (ICRAF 1995). Because tropical forests may support as much as 70% of the planet’s plant and animal species, deforestation in the tropics represents the greatest single threat to global biodiversity. Deforestation is proceeding most rapidly in those countries holding the planet’s richest biodiversity (Balmford & Long 1994). An estimated 109 ha of land (an area approximately equal to all the planet’s remaining tropical forests; Mayaux et al. 1998) may be cleared for cultivation in the developing world by 2050, mostly in Latin America and subSaharan Africa (Tilman et al. 2001). The external impacts of agriculture, such as water and air pollution, could affect even larger areas. Forest clearance by burning accounts for 25% of total CO2 emissions, making it a major contributor to global climate change (Newmark 1998). Agriculture is an anthropogenic threat to biodiversity that can adversely affect vast areas (e.g., Donald et al. 2001). There are significant conservation implications of agricultural production systems that go beyond their replacement of natural habitats. In many systems, management spans a gradient from low to high intensity. A growing number of consumers in the developed world are prepared to pay a premium to encourage less intensive forms of production in the belief that these have environmental benefits. Quantifying these benefits and identifying the important ecosystem properties of such systems, however, is not easy. The extent to which particular commodity production systems are deemed beneficial or deleterious to the conservation of biodiversity is at least partly subjective. The conversion of natural habitats to commodity production, however sympathetically managed, is likely to result in a loss of biodiversity. On the other hand, environmentally sustainable forms of commodity production are often regarded as valuable habitats in their own right and greatly preferable to other forms of habitat exploitation. Whether habitat conversion to agricultural commodity systems or the subsequent intensification of those systems has the greater environmental impact is unclear, but is likely to differ between crops. Consumers in the developed world are becoming increasingly aware of the environmental advantages of lowintensity production and are prepared to pay a premium on produce from such systems. The next few years are likely to be influential in developing the planet’s long-term agricultural and environmental policies (Crompton & Hardstaff 2001) and in determining the buying patterns of consumers in the developed world of products grown in the developing world for export (Donald et al. 2004), so a review of current knowledge is timely. I reviewed published and unpublished scientific evidence to assess and quantify the environmental implications of several important agricultural commodity production systems. These were chosen to encompass a range of product types (oils, grain, and fruits) grown mainly for export in areas of rich biodiversity where systems of production have changed radically during recent decades. All are regarded as potential threats to biodiversity in at least some parts of their range. A number of other crops, such as tea (Camillia sinensis L.) and rubber (Hevea brasiliensis [Willd.] Muell.Arg.), would have fulfilled these criteria, but too little quantitative information on biodiversity in these crops was available to permit any general conclusions (though see Wu et al. 2001; Schroth et al. 2003). A specific aim of my review is to identify research priorities.

Diclofenac poisoning as a cause of vulture population declines across the Indian subcontinent

Abstract: Summary 1 Rapid population declines of the vultures Gyps bengalensis, Gyps indicus and Gyps tenuirostris have recently been observed in India and Pakistan, continuing at least up to 2003 Surveys indicate annual rates of decline of 22–50% for G bengalensis and G indicus during 2000–03 Previous studies in Pakistan have shown that the non-steroidal anti-inflammatory drug diclofenac causes renal failure and is lethal to G bengalensis when it feeds on the carcass of a domestic animal that received a normal veterinary dose shortly before death In Pakistan, diclofenac poisoning was found to be by far the most frequent cause of death 2 A simulation model of vulture demography, described in this paper, demonstrated that the observed rates of population decline could be caused by contamination with a lethal level of diclofenac in a small proportion (between 1 : 130 and 1 : 760) of ungulate carcasses available to vultures 3 Proportions of adult and subadult vultures found dead or dying in the wild that had signs of diclofenac poisoning were similar to the proportions of deaths expected from the model if the observed population decline was due entirely to diclofenac poisoning The proportion of the excess mortality required to cause the observed population declines that could be attributable to diclofenac was estimated to be between 71% and 100%, depending on model assumptions However, across all or most of the plausible range of assumed values for adult survival, the upper 95% confidence limit for the proportion of excess mortality due to diclofenac was 100% Hence, available data are consistent with diclofenac poisoning being at least the major cause, and possibly the only cause, of rapid population declines of Gyps vultures across the Indian subcontinent 4 Synthesis and applications We recommend that urgent action is taken in the range states of the three currently threatened vulture species to prevent the exposure of vultures to livestock carcasses contaminated with diclofenac Research is also needed to identify alternative drugs that are effective in livestock and safe for vultures Efforts should also be made to raise awareness, among veterinarians, pharmacists, livestock owners and the general public, of the problem of diclofenac contamination and the availability of safe alternatives Captive holding and breeding of vultures until diclofenac is controlled is recommended as a precaution to ensure the long-term survival of the threatened species and to provide a stock of birds for future reintroduction programmes

Diclofenac poisoning is widespread in declining vulture populations across the Indian subcontinent.

Abstract: Recent declines in the populations of three species of vultures in the Indian subcontinent are among the most rapid ever recorded in any bird species. Evidence from a previous study of one of these species, Gyps bengalensis, in the Punjab province of Pakistan, strongly implicates mortality caused by ingestion of residues of the veterinary non-steroidal anti-inflammatory drug diclofenac as the major cause of the decline. We show that a high proportion of Gyps bengalensis and G. indicus found dead or dying in a much larger area of India and Nepal also have residues of diclofenac and visceral gout, a post-mortem finding that is strongly associated with diclofenac contamination in both species. Hence, veterinary use of diclofenac is likely to have been the major cause of the rapid vulture population declines across the subcontinent.

The state of play of farmland birds: population trends and conservation status of lowland farmland birds in the United Kingdom

Abstract: Many bird species of lowland farmland have declined substantially in the United Kingdom over the past 30 years. Declines among farmland specialists are steeper than for generalists and were most rapid for these specialists in the 1970s and 1980s. These changes have been linked to increased agricultural intensification and are reflected in Red or Amber conservation concern status for many common farmland species, as well as for rarer ones. We review long- and short-term population trends and the conservation status of lowland farmland birds in the UK using the latest available information from bird surveys, and examine patterns among species. Analyses of demographic parameters suggest broadly that the key factor driving population changes of seed-eating and migrant birds is overwinter survival, whereas for many non-passerine species population growth appears to be limited by productivity. Population trends for a suite of lowland farmland species were first combined in the UK Government's headline wild bird indicator published in 1998. This ‘Skylark index’ as it is sometimes known was intended to reflect the health of the wider countryside and struck a chord with the public and decision-makers. We look at the behaviour of the composite indicator and explore the population dynamics of the increasing and declining species separately. Simple models of population growth in these groups are then used to explore plausible scenarios for delivering the Government's Public Service Agreement target to reverse the long-term decline in the number of farmland birds by 2020.

Evidence for the indirect effects of pesticides on farmland birds

Abstract: Indirect effects of pesticides, operating through the food chain, have been proposed as a possible causal factor in the decline of farmland bird species. To demonstrate such a link, evidence is needed of (1) an effect of food abundance on breeding performance or survival; (2) an effect of breeding performance or survival on population change; and (3) pesticide effects on food resources, sufficient to reduce breeding performance or survival, and hence to affect the rate of population change. Evidence under all three categories is only available for one species, the Grey Partridge Perdix perdix, although data showing effects of pesticides on food resources and relationships between food resources and breeding performance are also available for some other species. This paper reports on recent work investigating the effects of pesticides on Yellowhammer Emberiza citrinella and Skylark Alauda arvensis during the breeding season. The probability of brood reduction in Yellowhammer was affected by the proportion of the foraging area around the nest which was sprayed with insecticide. No significant effects of pesticides were recorded on Skylark chick condition or growth rate, but sample sizes were small. Invertebrate food abundance affected chick condition (Skylark) and the number of chicks fledging (Yellowhammer and Corn Bunting Miliaria calandra; relationship for the latter derived from re-analysis of data from an earlier study). Other recent work is briefly reviewed and the current evidence for the indirect effects of pesticides is summarized. Significant knowledge gaps are identified and some of the issues involved in resolving these are discussed.

The performance of models relating species geographical distributions to climate is independent of trophic level

Abstract: Species–climate ‘envelope’ models are widely used to evaluate potential climate change impacts upon species and biodiversity. Previous studies have used a variety of methods to fit models making it difficult to assess relative model performance for different taxonomic groups, life forms or trophic levels. Here we use the same climatic data and modelling approach for 306 European species representing three major taxa (higher plants, insects and birds), and including species of different life form and from four trophic levels. Goodness-of-fit measures showed that useful models were fitted for >96% of species, and that model performance was related neither to major taxonomic group nor to trophic level. These results confirm that such climate envelope models provide the best approach currently available for evaluating reliably the potential impacts of future climate change upon biodiversity.

What factors determine where invertebrate‐feeding birds forage in dry agricultural grasslands?

Abstract: Increases in the intensity of the management of agricultural grasslands over the past 50 years have reduced plant species diversity in swards and increased uniformity in structure through changes in fertilizer regimes, grazing and mowing practices. These factors, as well as increased disturbance and trampling, have reduced the number and diversity of forbs and thus the diversity and abundance of invertebrates, in particular of foliar species. Associated with these changes in management, there has been a large decline in the abundance of many species of farmland birds in pastoral areas and more local extinctions compared with arable areas. To understand the impact of these management changes on bird populations, and design measures to reverse the declines, it is necessary to identify the key factors influencing bird usage of fields. We review results from five studies, which have related fertilizer and grazing management to bird usage of grass fields. Species that fed on soil invertebrates tended to show a positive response to the amount of nitrogen fertilizer added and increased grazing pressure, although there was a high degree of correlation between these two variables. In summer, many species, including corvids, Common Blackbird Turdus merula, Common Starling Sturnus vulgaris, Pied Wagtail Motacilla alba and Hedge Accentor Prunella modularis, showed a negative relationship with sward height, and in winter more species showed a positive relationship with bare ground. Taller sward heights are associated with a greater abundance and diversity of bird invertebrate food resources, and accessibility of food items or a lower risk of predation (actual or perceived) are likely to be the reasons for birds choosing to forage on shorter swards and in areas with more bare ground. Birds feeding on soil invertebrates were found to be generally tolerant of modern management practices that maintain short swards short, as accessibility to the soil has been increased. Species that feed on foliar invertebrates or forb seeds have been affected negatively by modern grassland agricultural practices.

Demographic mechanisms of the population decline of the song thrush Turdus philomelos in Britain

Abstract: In Britain, the song thrush Turdus philomelos is categorized as a species of high national conservation concern because of a large population decline during the last three decades. We calculated a series of annual national population estimates for woodland and farmland habitats combined for the period 1964-2000. We then used turning points analysis to identify seven blocks of years within the period of decline (1968-2000) with uniform rates of population change in the smoothed trend. 2. We used recoveries of song thrushes ringed as nestlings, juveniles and adults during April-September to estimate survival rates separately for the post-fledging period, the remainder of the first year and for adults. Daily survival probability was lower during the post-fledging period than during the remainder of the first year or for older birds. 3. There was evidence for variation in survival rates among blocks of years with different rates of population change, particularly for first-year survival. There were significant positive correlations across blocks between mean population multiplication rate (PMR) and both post-fledging and first-year survival. 4. Survival of first-year birds was correlated negatively with the duration of the longest run of frost days and the survival of adults was correlated negatively with the duration of the longest summer drought. Variation among blocks in mean PMR was correlated with block means of the duration of runs of frost days and drought days, but significant correlations between PMR and both post-fledging and first-year survival remained after allowing for the influence of weather on survival. 5. Changes in survival in the first winter, and perhaps also the post-fledging period, are sufficient to have caused the song thrush population decline. The environmental causes of these changes are not known, but changes in farming practices, land drainage, pesticides and predators are all candidates. Adverse weather conditions contributed to the decline, but were not the primary driver. [KEYWORDS: demographic models juvenile mortality population change ringing recoveries survival rates]

An experimental study of the effects of predation on the breeding productivity of capercaillie and black grouse

Abstract: Summary 1 The capercaillie Tetrao urogallus and black grouse Tetrao tetrix are declining in the UK, and low breeding success has been identified as the key factor in the decline of the former. To investigate possible causes, breeding productivity was studied in relation to predation, weather, vegetation changes and deer numbers over an 11-year period (1989–99) within native pinewood at Abernethy Forest, Scotland. The abundance of predators (crows Corvus corone and red foxes Vulpes vulpes) was experimentally manipulated in 1992–96 by culling. Productivity (chicks reared per female) was compared between forests with and without experimental predator management. 2 During predator control, the number of breeding crows was reduced from 10 pairs to one. The attempted reduction in red fox abundance was unsuccessful; only small numbers of adults were killed, and neither scat nor den counts declined significantly. 3 Predation on artificial nests containing six hen eggs and a hen egg filled with wax was measured as an index of predator activity from 1991 to 1999. Predation was lowest during the last three years of predator control, 1994–96. Predators could sometimes be distinguished by signs on depredated eggs. Predation on artificial nests by crows was highest during 1991–93. However, after predator removal stopped in 1997 few crows returned, and increased predation on artificial nests did not involve increased signs of crow predation. Pine marten Martes martes numbers increased during the study period and became significant predators of artificial nests. 4 The total number of capercaillie eggs and nests depredated by crows was estimated from the number of depredated capercaillie eggs found and the proportion of crow-predated hen eggs in artificial nests. The values ranged from 18 to 158 eggs over 3 years, equivalent to 3–23 capercaillie nests year−1. 5 Capercaillie productivity was low (< 1 chick per female) during 1989–93 and 1997–99 but higher during 1994–96. Compared with nine other forests in Scotland, changes in capercaillie productivity at Abernethy were different. Productivity at Abernethy was negatively related to June rainfall, and to the minimum daily predation rate on artificial nests by crows. There was also a significant interaction in that capercaillie were most productive when low rainfall coincided with low predation by crows on artificial nests. 6 The productivities of black grouse and capercaillie were positively correlated, but greater in the former. As in capercaillie, black grouse productivity was negatively related both to June rainfall and the minimum daily predation rate on artificial nests by crows, and there was an interaction. 7 Synthesis and applications. The long-term increase in crows and red foxes and the predicted increase in rainfall in Scotland may have negative effects on capercaillie and black grouse. In the short term, control of crows is likely to improve productivity. In the long term, increased woodland size and some reversal of fragmentation might decrease the access to woodland of predators associated with the interface between farmland and woodland.

Sustainable Arable Farming For an Improved Environment (SAFFIE): managing winter wheat sward structure for Skylarks Alauda arvensis

Abstract: Research has shown a close correlation between the decline of the UK Skylark Alauda arvensis population and the replacement of spring-sown cereals with winter-sown varieties, in which advanced sward development prevents successful multiple nesting attempts and reduces access for foraging. Widescale reversal of sowing times is unlikely for commercial reasons, so research has recently focused on ways of manipulating the sward structure of winter wheat to prolong access to nest-sites and food. An RSPB pilot study investigated leaving small ‘undrilled patches’ in otherwise conventionally managed winter wheat crops. This option was later incorporated into a fully replicated experimental design, as part of the Sustainable Arable Farming For an Improved Environment (SAFFIE) project. This large consortium-led project aims to test solutions for improving biodiversity within winter-cereal-dominated rotations. The experiment described here ran over 2002–3, with three field-scale ‘treatments’ on 15 sites in the first year. The treatments compare (1) conventional winter wheat, (2) winter wheat sown in double-normal width (25 cm) wide-spaced rows (WSR) and (3) winter wheat with two 4-m by 4-m undrilled patches per hectare (UP). Results from the 2002 breeding season showed that undrilled patch treatments supported more breeding Skylarks for longer, most likely by aiding accessibility of food. WSR rows were little used by Skylarks and did not improve the abundance of favoured seed and invertebrate food items over conventional crops. Nesting performance and foraging patterns are discussed with reference to invertebrate food abundance and its accessibility, as determined by sward structure.

Using stable isotopes to investigate migratory connectivity of the globally threatened aquatic warbler Acrocephalus paludicola

Abstract: Understanding the links between breeding and wintering areas of migratory species has important ecological and conservation implications. Recently, stable isotope technology has been used to further our understanding. Stable isotope ratios vary geographically with a range of biogeochemical factors and isotope profiles in organisms reflect those in their food and environment. For inert tissues like feathers, isotope profiles reflect the environment in which they were formed. Following large-scale habitat destruction, the globally threatened aquatic warbler Acrocephalus paludicola has a fragmented breeding population across central Europe, largely in Belarus, Poland and Ukraine. The species’ sub-Saharan African wintering grounds have not yet been discovered, and this significantly hampers conservation efforts. Aquatic warblers grow their flight feathers on their wintering grounds, and we analysed stable isotope ratios (δ15N, δ13C, δD) in rectrices of adults from six main breeding sites (subpopulations) across Europe to determine whether different breeding subpopulations formed a single mixed population on the wintering grounds. δ15N varies considerably with dietary trophic level and environmental factors, and δD with the δD in rainfall; neither varied between aquatic warbler subpopulations. Uniform feather δ15N signatures suggest no major variation in dietary trophic level during feather formation. High variance and inter-annual differences in mean δD values hinder interpretation of these data. Significant differences in mean δ13C ratios existed between subpopulations. We discuss possible interpretations of this result, and consider differences in moulting latitude of different subpopulations to be the most parsimonious. δ13C in plants and animals decreases with latitude, along a steep gradient in sub-Saharan Africa. Birds from the most north-westerly breeding subpopulation (Karsibor, Poland) had significantly lower variance in δ13C and δ15N than birds from all other sites, suggesting either that birds from Karsibor are less geographically dispersed during moult, or moult in an area with less isotopic heterogeneity. Mean δ13C signatures from winter-grown feathers of different subpopulations were positively correlated with the latitude and longitude of breeding sites, suggesting a strong relationship between European breeding and African winter moulting latitudes. The use of stable isotopes provides novel insights into migratory connectivity and migration patterns in this little-known threatened species.

Changes in breeding wader populations on lowland wet grasslands in England and Wales: causes and potential solutions

Abstract: Populations of waders breeding on lowland wet grassland in England and Wales have declined markedly in recent decades; the loss of once widespread species such as Lapwing Vanellus vanellus, Snipe Gallinago gallinago and Redshank Tringa totanus from many areas is of particular conservation concern These declines are due to loss of grassland to other land uses, and to significant changes in grassland management Drainage, reseeding and changes in grazing regimes have all been particularly detrimental to lowland wet grassland in terms of a breeding habitat for waders Careful management of key sites, many of them managed as nature reserves, has shown that wader declines can be halted or even reversed Aspects of this management can be applied to larger areas through agri-environment schemes, such as the Environmentally Sensitive Areas (ESA) scheme, Tir Gofal (in Wales) and Countryside Stewardship (in England) but these need be carefully targeted to ensure that the benefits for waders are maximized In particular, it has been shown that higher tier management options within the ESA scheme (those that enhance the landscape) are more cost-effective than lower tier options (those that maintain the landscape) The extent and suitability of lowland wet grassland will face further pressure in years to come as a result of climate change, the impacts of which need to be assessed and mitigated against

Habitat selection by song thrushes in stable and declining farmland populations

Abstract: Summary 1 Losses of farmland birds from the wider countryside have become a major conservation issue in the UK and Europe. Song thrush Turdus philomelos populations in lowland rural Britain declined by approximately 70% during 1970–95, most severely on intensively managed arable farmland. Comparison between a stable population on mixed farmland and a rapidly declining population on arable farmland revealed fewer nesting attempts each summer by birds in the declining population, and annual productivity was insufficient to maintain local population density. Inadequate food resources were the most plausible cause. 2 We compared breeding season habitat selection (using radio-telemetry) and earthworm availability (a major component of summer diet) for song thrushes in the same two farmland populations. 3 Territory settlement in the mixed farmland landscape involved the selection of field boundaries and woodland and the avoidance of arable crops. Field boundaries and gardens were selected in the arable landscape, while arable break crops and small areas of woodland were avoided. 4 Habitat selection (intensity of usage) did not change through the breeding season and did not differ between study areas. Scrub, woodland edge, wet ditches and bare soil in gardens were preferred foraging habitats, while cereals were avoided. 5 Habitat utilization (amount of usage) differed markedly between study areas. Woodland and grassland accounted for 53% of all habitat usage in the mixed farmland landscape compared with just 13% in the arable landscape. Gardens and arable crops were more heavily utilized in the arable landscape, accounting for 58% of all usage compared with 22% in the mixed landscape. 6 Earthworm availability declined markedly between April and June as surface soils dried out. Lower earthworm availability in the arable landscape was associated with more rapid and pronounced drying of surface soils. 7 Synthesis and applications. Lack of woodland and grassland, and the faster drying of surface soils in the arable landscape, combined to limit the availability to thrushes of key summer invertebrate prey. Loss of hedgerows, scrub and permanent grassland with livestock, and the wide-scale installation of under-field drainage systems, have probably all contributed to the decline of song thrushes on UK arable farmland. New agri-environment measures may be needed to provide the nesting cover adjacent to invertebrate-rich damp soils that song thrushes require to sustain annual productivity.

Reproductive consequences for great skuas specializing as seabird predators

Abstract: Most of the Great Skuas (Stercorarius skua) breeding at Hermaness, Shetland, exhibit dietary specialization: a small proportion feed almost exclusively upon seabird prey, a small proportion feed as generalists, and most feed on fishery discards We investigated the foraging dynamics, reproductive performance, and survival of Great Skuas that specialized in depredating other seabirds compared with those feeding predominantly on fish Around half of the specialist bird predators defended combined breeding and feeding territories that included a section of seabird colony; the remainder of the predatory skuas foraged away from breeding territories Specialist bird predators retained their feeding habit and, if present, feeding territory, across years Time budgets revealed that specialist bird predators spent less time foraging than skuas feeding predominantly on fish Results of radio-telemetry indicated that bird-specialist skuas have smaller home ranges than other birds In a comparison of reprodu

Land‐use trends in Endemic Bird Areas: global expansion of agriculture in areas of high conservation value

Abstract: The impacts of humans on biodiversity tend to be exacerbated by the coincidence of human settlement with areas of high biological value, as demonstrated by regional, continental and global analyses. We present a global analysis, intersecting Endemic Bird Areas (EBAs) with fine-scale data on changes in agricultural land use for the past 300 years and for four scenarios projecting land use up to 2050. The proportion of land in agricultural use is currently greater in EBAs than in the rest of the world (42.0% vs. 37.0%, respectively), has been historically (in 1700: 9.1% vs. 5.7%, through to 1900: 43.4% vs. 32.1%) and looks set to remain so in the future (44.6-56.1% vs. 37.0-43.2%; depending on scenario). However, the future course of agricultural expansion is more scenario-dependent in EBAs than in the rest of the world, indicating that development policies have considerable potential to either ease or exacerbate the disproportionate impact of agriculture on areas of highest biological value.

Modelling habitat selection and distribution of the critically endangered Jerdon's courser Rhinoptilus bitorquatus in scrub jungle: an application of a new tracking method

Abstract: 1. Jerdon's courser Rhinoptilus bitorquatus is a nocturnally active cursorial bird that is only known to occur in a small area of scrub jungle in Andhra Pradesh, India, and is listed as critically endangered by the IUCN. Information on its habitat requirements is needed urgently to underpin conservation measures. We quantified the habitat features that correlated with the use of different areas of scrub jungle by Jerdon's coursers, and developed a model to map potentially suitable habitat over large areas from satellite imagery and facilitate the design of surveys of Jerdon's courser distribution. 2. We used 11 arrays of 5-m long tracking strips consisting of smoothed fine soil to detect the footprints of Jerdon's coursers, and measured tracking rates (tracking events per strip night). We counted the number of bushes and trees, and described other attributes of vegetation and substrate in a 10-m square plot centred on each strip. We obtained reflectance data from Landsat 7 satellite imagery for the pixel within which each strip lay. 3. We used logistic regression models to describe the relationship between tracking rate by Jerdon's coursers and characteristics of the habitat around the strips, using ground-based survey data and satellite imagery. 4. Jerdon's coursers were most likely to occur where the density of large (>2 m tall) bushes was in the range 300-700 ha(-1) and where the density of smaller bushes was less than 1000 ha(-1). This habitat was detectable using satellite imagery. 5. Synthesis and applications. The occurrence of Jerdon's courser is strongly correlated with the density of bushes and trees, and is in turn affected by grazing with domestic livestock, woodcutting and mechanical clearance of bushes to create pasture, orchards and farmland. It is likely that there is an optimal level of grazing and woodcutting that would maintain or create suitable conditions for the species. Knowledge of the species' distribution is incomplete and there is considerable pressure from human use of apparently suitable habitats. Hence, distribution mapping is a high conservation priority. A two-step procedure is proposed, involving the use of ground surveys of bush density to calibrate satellite image-based mapping of potential habitat. These maps could then be used to select priority areas for Jerdon's courser surveys. The use of tracking strips to study habitat selection and distribution has potential in studies of other scarce and secretive species.

Predation by great skuas at a large Shetland seabird colony

Abstract: Summary 1. Skuas are top predators in marine ecosystems and may have detrimental effects on seabird communities they prey upon. However, predation rates are poorly understood and poorly quantified. Using a bio-energetics model we estimate seabird predation by great skuas, Stercorarius skua , at a large UK colony (Hermaness, Shetland). We investigate the influence of dietary specialization and fishery management on predation and explore the effect of experimental removal of specialist bird predators. 2. Great skuas at Hermaness required 491·5 × 10 6 kJ and 546·6 × 10 6 kJ of energy in each of two breeding seasons. Breeding skuas fell into one of two groups: a small proportion (5%) of specialist bird predators or the vast majority (95%) that fed opportunistically on birds or specialized on fishery discards. During 1999, great skuas consumed ≈ 80 000 kg of fish, which increased to over 90 000 kg in 2001. About 13 000 seabirds were consumed by great skuas each year, with 26‐29% being consumed by specialist bird predators. 3. Although it is difficult to assess, great skuas appear to be having a negative impact on seabird populations. Altering model inputs to test differing scenarios revealed that reductions in fishery discards would result in increased seabird predation rates. However, proposed changes in fishery management over the period of the study did not reduce discarding rates, which instead increased. 4. Synthesis and applications . The use of a bioenergetics model reveals that great skua predation may negatively affect seabird populations. Availability of fishery discards is an important factor influencing seabird predation rates, but predicting the effect of changes in fishery management may be difficult in the short term. Specialist bird predators consume large quantities of seabird prey, but this is less significant at the population level. Although experimental removal of specialist bird predators may reduce predation at a minimal loss of skuas, it is unclear whether conspecifics may replace them and retain high rates of predation.

Policy into practice: the development and delivery of agri‐environment schemes and supporting advice in England

Abstract: There has been significant progress in recent years in translating the knowledge gained from farmland bird research into mechanisms which deliver sympathetic farm management. This progress is described for England, focusing on the development, targeting and delivery of agri-environment schemes and supporting advisory materials and services. Following the successful implementation and evaluation of the Arable Stewardship Pilot Scheme, modified arable land management options were introduced into the Countryside Stewardship Scheme in 2002, targeted at scarce farmland birds and other threatened farmland wildlife. An enhanced suite of options will be introduced in 2005 in a new scheme, Environmental Stewardship, encompassing both simple ‘Entry Level’ and more demanding ‘Higher Level’ options. The former were piloted successfully in 2003, while the latter will replace existing schemes and focus more on defined environmental outcomes. The valuable synergies and contributions of partnerships in developing, targeting and evaluating schemes is acknowledged. Recognizing the targeting value of recent distribution data for declining farmland bird species, a project is underway to collate recent records and to make interpreted data accessible to farmers and their advisers. Appropriate advisory materials and demonstration sites have been used to engage and motivate farmers, by providing feedback, a sense of pride and better public appreciation. Examples of best practice in knowledge transfer are given: individually tailored advice and the use of suitable demonstration farms are very powerful mechanisms for achieving environmental results, but are costly. The policy and advisory infrastructure currently in place, across and between government and the voluntary sector, provides an unprecedented basis for an optimistic outlook for farmland birds.

Five-year evaluation of the impact of the Arable Stewardship Pilot Scheme on birds

Abstract: Agri-environment schemes could play a key role in the reversal of farmland bird declines. The effectiveness of the Arable Stewardship Pilot Scheme for delivering farmland birds was tested in a replicated, farm-scale field trial, in two lowland farmland regions of England. Changes in numbers of birds over five years were compared between control and scheme farms. In East Anglia, productivity of Grey Partridges Perdix perdix was significantly higher on scheme than on control farms, although such an effect was not seen in the West Midlands where the species was rarer. At the field scale, wintering granivorous passerines and Skylarks Alauda arvensis responded to stewardship habitats (options) such as stubble and wild bird cover designed specifically to benefit them. However, at the farm scale, winter bird counts were higher on scheme than control farms only in the West Midlands, and not in East Anglia where the availability of set-aside and features managed for game in the wider landscape was higher. In the absence of other high-quality habitat, arable options are effective at providing good quality habitat, but the amount needed to exert an influence at the bird population level remains uncertain.

Managed realignment in the UK – the first 5 years of colonization by birds

Abstract: With current losses of saltmarsh running at > 100 ha per year in the UK, creation of new intertidal habitats through managed realignment is likely to be increasingly used. Potentially, this has biodiversity as well as engineering benefits. However, assessing the conservation value of many of the current UK schemes is difficult as the biological monitoring has been generally poor, with a few notable exceptions. At the Tollesbury and Orplands realignment sites, Essex, bird communities were dominated by terrestrial species during the first year of inundation and waterbird communities rapidly developed during the second and third years. Five years after the initial breach in the sea wall, communities were similar to surrounding mudflats but with some notable exceptions. Dunlin Calidris alpina and Common Redshank Tringa totanus that prey on the early colonizing Nereis and Hydrobia used the sites in the first 2 years. Eurasian Oystercatcher Haematopus ostralegus did not occur on the realignment site as there were no large bivalves, whereas Red Knot Calidris canutus used the site after 4–5 years coincidentally with the appearance of Macoma balthica. The differences in the bird communities occurred because UK sites are often small, enclosed and poorly drained. If at a suitable height in the tidal frame, UK managed realignment sites are successful in that they have developed saltmarsh and biologically active mudflats but they may lack the full range of biodiversity found in surrounding natural intertidal habitats, even decades after inundation.

Habitat use by breeding Tree Sparrows Passer montanus

Abstract: Tree Sparrows Passer montanus showed a strong preference for nest-sites adjacent to wetland habitats, and avoidance of sites on intensively managed mixed farmland distant from Rutland Water A variety of wetland edge habitats were frequently used by foraging adult birds when provisioning nestlings, and invertebrate prey of aquatic origin was frequently recorded in chick diet We suggest that the wetland edge habitats at the study sites played a key role in providing adequate diversity and availability of suitable invertebrate prey to allow successful chick rearing throughout the long breeding season of this multi-brooded passerine It is possible that large areas of formerly occupied farmland in the UK no longer provide these invertebrate resources due to the effects of intensification in the late 20th century There was no evidence that the availability of supplementary seed food within 1 km of the nest-site influenced nest-site choice, or affected productivity It is probable that the importance of seed food resources to the persistence of Tree Sparrow populations operates on a larger spatial scale than that tested in this study, due to the greater mobility of Tree Sparrows in the non-breeding season, when seed resources are most likely to be a key limiting factor When considering conservation management aimed at recovering breeding populations of Tree Sparrows, the key resources of seed food, invertebrate food and nest-sites must be made available at appropriate spatial scales

Breeding biology of the Atlantic Petrel, Pterodroma incerta, and a population estimate of this and other burrowing petrels on Gough Island, South Atlantic Ocean

Abstract: The Atlantic Petrel, Pterodroma incerta, endemic to the Tristan da Cunha group in the South Atlantic and globally threatened, is one of the least known of the world's seabirds. At Gough Island, Atlantic Petrels are winter breeders, with single eggs laid in June–July and chicks fledging in December. Birds were exclusively nocturnal on land. The pre-egg exodus of ~50 days and nestling period of almost 140 days are near the longest recorded for Pterodroma species, and support the general pattern of prolonged development found in winter-breeding Procellariiformes. Chicks grew at a very slow rate, suggesting poor at-sea feeding conditions. Breeding success averaged only 20% and introduced House Mice, Mus musculus, were probably responsible for considerable losses of chicks in two breeding seasons. Preliminary population modelling predicts a decline in numbers. The potential impact of introduced mice suggests that the species' conservation status be upgraded from Vulnerable to Endangered and that further research on this issue is a high priority. The first quantitative estimate of breeding numbers indicates a population of ~1.8 million pairs of Atlantic Petrels. Provisional population estimates of Great Shearwaters, Puffinus gravis (980 000 pairs), Soft-plumaged Petrels, Pterodroma mollis (400 000 pairs), and Broad-billed Prions, Pachyptila vittata (1 750 000 pairs) confirm the international significance of Gough Island as a site for breeding seabirds.

Demographic and environmental causes of the decline of rural Song Thrushes Turdus philomelos in lowland Britain

Abstract: We review current knowledge of demographic mechanisms and environmental factors implicated in the population decline of Song Thrushes Turdus philomelos in rural Britain since the mid-1970s, and present new analyses of regional variation in population changes Increased mortality during the first year of life (from fledging to recruitment) is highlighted as a potential demographic mechanism having driven the population decline, while Song Thrushes in a rapidly declining farmland population were making too few nesting attempts to sustain local numbers Breeding Song Thrushes are strongly associated with non-cropped habitats such as woodland edge, field boundaries, gardens and scrub; they make substantial use of grassland, but avoid cereals when foraging Earthworms constitute a key component of Song Thrush diet and the availability of this prey is strongly influenced by moisture levels in surface soils Several lines of evidence suggest that dry surface soils during summer are deleterious to the productivity and survival of Song Thrushes, and regional variation in the rates of population change in Britain during 1970–86 was negatively correlated with the extent of under-field drainage on farmland (the main function of which is to promote the drying of surface soils) Increasing dryness of agricultural soils and the loss of grassland from eastern arable counties have probably both contributed to the declines of rural Song Thrushes in Britain Loss of hedgerows and scrub, and the degradation of woodland may also have contributed to population declines but the role of predators remains unclear Recovery of rural Song Thrush populations requires challenging new policy initiatives that should aim to restore nesting cover (scrub and woodland understorey), grazed grassland in arable-dominated areas and damper soils in summer

Non-inversion tillage and farmland birds: a review with special reference to the UK and Europe

Abstract: This paper reviews the current knowledge of the effects of non-inversion tillage (NIT) on farmland birds and their food resources. NIT is a method of establishing a crop without using a mouldboard plough and is becoming increasingly popular in the UK. NIT generally disturbs the soil to shallower depths than conventional tillage and is therefore expected to have beneficial effects on biodiversity on arable land as compared with mouldboard ploughing. The diets of farmland birds change throughout the year, and many species take invertebrates over the breeding season. Seeds are also important for many species of farmland birds throughout the year and especially over the winter months. The effects of NIT on these farmland bird food resources, in particular ground beetles (Coleoptera: Carabidae), spiders (Arachnida: Araneae), earthworms (Annelida) and seeds (arable weeds and cereal crops) are reviewed.

The breeding ecology of Reed Buntings Emberiza schoeniclus in farmland and wetland habitats in lowland England

Abstract: We studied the nesting and feeding ecology of Reed Buntings Emberiza schoeniclus breeding on farmland and wetland habitats along the Trent Valley in Nottinghamshire, England. Rank and emergent vegetation accounted for most nests and most foraging by provisioning adults. Caterpillars and spiders accounted for 70% of chick invertebrate prey and all broods were fed cereal grain or other vegetable matter. Variation in the abundance of key invertebrate prey across habitats accounted for the foraging preferences of adult buntings. Depredation was the main cause of nest failure, and survival of nests at the egg stage was positively related to the extent of nest concealment. A measure of total brood biomass was positively related to the abundance of key invertebrate prey within 100 m of nests. Rank and emergent vegetation provided Reed Buntings with greater nest concealment and a richer source of invertebrate prey than agricultural habitats such as set-aside, cereals and oilseed rape. The provision of rank and emergent vegetation on farmland is likely to increase the nesting opportunities and productivity of Reed Buntings in agricultural landscapes.