G. Siriwardena

The second Silent Spring

The drive to squeeze ever more food from the land has sent Europes farmland wildlife into a precipitous decline. How can agricultural policy be reformed so that we have fewer grain mountains and more skylarks?

Bringing Ecosystem Services into Economic Decision-Making: Land Use in the United Kingdom

Monitoring Land Use Land-use decisions are based largely on agricultural market values. However, such decisions can lead to losses of ecosystem services, such as the provision of wildlife habitat or recreational space, the magnitude of which may overwhelm any market agricultural benefits. In a research project forming part of the UK National Ecosystem Assessment, Bateman et al. (p. 45) estimate the value of these net losses. Policies that recognize the diversity and complexity of the natural environment can target changes to different areas so as to radically improve land use in terms of agriculture and greenhouse gas emissions, recreation, and wild species habitat and diversity. The value of using land for recreation and wildlife, not just for agriculture, can usefully factor into planning decisions. Landscapes generate a wide range of valuable ecosystem services, yet land-use decisions often ignore the value of these services. Using the example of the United Kingdom, we show the significance of land-use change not only for agricultural production but also for emissions and sequestration of greenhouse gases, open-access recreational visits, urban green space, and wild-species diversity. We use spatially explicit models in conjunction with valuation methods to estimate comparable economic values for these services, taking account of climate change impacts. We show that, although decisions that focus solely on agriculture reduce overall ecosystem service values, highly significant value increases can be obtained from targeted planning by incorporating all potential services and their values and that this approach also conserves wild-species diversity.

Bringing ecosystem services into economic decision-making

Monitoring Land Use Land-use decisions are based largely on agricultural market values. However, such decisions can lead to losses of ecosystem services, such as the provision of wildlife habitat or recreational space, the magnitude of which may overwhelm any market agricultural benefits. In a research project forming part of the UK National Ecosystem Assessment, Bateman et al. (p. 45) estimate the value of these net losses. Policies that recognize the diversity and complexity of the natural environment can target changes to different areas so as to radically improve land use in terms of agriculture and greenhouse gas emissions, recreation, and wild species habitat and diversity. The value of using land for recreation and wildlife, not just for agriculture, can usefully factor into planning decisions. Landscapes generate a wide range of valuable ecosystem services, yet land-use decisions often ignore the value of these services. Using the example of the United Kingdom, we show the significance of land-use change not only for agricultural production but also for emissions and sequestration of greenhouse gases, open-access recreational visits, urban green space, and wild-species diversity. We use spatially explicit models in conjunction with valuation methods to estimate comparable economic values for these services, taking account of climate change impacts. We show that, although decisions that focus solely on agriculture reduce overall ecosystem service values, highly significant value increases can be obtained from targeted planning by incorporating all potential services and their values and that this approach also conserves wild-species diversity.

ANALYSIS OF POPULATION TRENDS FOR FARMLAND BIRDS USING GENERALIZED ADDITIVE MODELS

Knowledge of the direction, magnitude, and timing of changes in bird population abundance is essential to enable species of priority conservation concern to be identified, and reasons for the population changes to be understood. We give a brief review of previous techniques for the analysis of large-scale survey data and present a new approach based on generalized additive models (GAMs). GAMs are used to model trend as a smooth, nonlinear function of time, and they provide a framework for testing the statistical significance of changes in abundance. In addition, the second derivatives of the modeled trend curve may be used to identify key years in which the direction of the population trajectory was seen to change significantly. The inclusion of covariates into models for population abundance is also discussed and illustrated, and tests for the significance of covariate terms are given. We apply the methods to data from the Common Birds Census of the British Trust for Ornithology for 13 species of farmland birds. Seven of the species are shown to have experienced statistically significant declines since the mid-1960s. Two species exhibited a significant increase. The population trajectories of all but three species turned downward in the 1970s, although in most cases the 1980s brought either some recovery or a decrease in the rate of decline. The majority of populations have remained relatively stable in the 1990s. The results are comparable with those from other analysis techniques, although the new approach is shown to have advantages in generality and precision. We suggest extensions of the methods and make recommendations for the design of future surveys.

Long-term variation in survival rates of Sand Martins Riparia riparia: dependence on breeding and wintering ground weather, age and sex, and their population consequences

Capsule Survival rates of Sand Martins are driven by variation in rainfall on the wintering grounds prior to their arrival and in the breeding area in the previous summer; inter-annual changes in abundance also show strong correlations with survival. Aims To investigate the demography underlying long-term changes in population size in a large study area in central England, focusing primarily on describing the variation in survival and identifying its causes and demographic consequences. Methods An intensive mark–recapture effort was undertaken on Sand Martin colonies in an area of over 400 km2 of Nottinghamshire, England, from 1967 to 1992. The resulting data were analysed using the program MARK to investigate variation in survival with respect to sex, age, time and variables describing the key climatic conditions on the breeding and wintering grounds. The same variables were also tested against data on the age-structure of the population. Results The average annual apparent survival probabilities of adult males and females were not significantly different (males 0.312 ± 0.026 se; females 0.289 ± 0.026 se). There was no obvious long-term temporal trend in survival rates, but considerable fluctuations occurred between years. There was a positive relationship between annual survival rates and Sahel rainfall, but a stronger, negative, relationship between survival and the previous summers rainfall in the study area. These relationships were reflected in correlations with the annual population level and the annual percentage change in the population, but other evidence suggests that rainfall on the breeding grounds during the breeding season has a further important effect on productivity. Conclusion The Sand Martin population in the study area was limited by climatic conditions, primarily rainfall in the breeding area, but also rainfall on the wintering grounds. These climatic effects operated mostly by influencing annual survival, but also probably affected productivity. This contrasts with published results for Sand Martins in central Europe, which have been found to be more strongly affected by rainfall on the wintering grounds and for which relationships between survival and abundance are obscured by fluctuations in immigration and emigration. The importance of rainfall on the breeding grounds as a negative influence on over-winter survival is a novel finding both in Sand Martin biology and in the context of the environmental influences on passerine demography in general.

Status and population trends of Starling Sturnus vulgaris in Great Britain

Capsule Starling populations have declined markedly since 1964, with the greatest declines in pastoral areas in the south and west of Britain. Aims To establish the size of the Starling population and its recent decline in different habitats and regions. Methods We use distance-based transect sampling to establish, for the first time, robust estimates of population size in different habitats and regions. We then analyse long-term trend data from two extensive monitoring schemes using generalized additive models to find correlates of the population decline. Results The mean national breeding population of Starling over the period 1994–2000 was estimated at about 8.5 million birds, with a 95% confidence interval of 8.1–10.8 million. Most Starlings (36%) occur in southern Britain and densities are greatest in suburban habitats. Populations in both suburban areas and the wider countryside declined by over 50% between 1964 and 2000, being greatest in the south and west of Britain and in areas of livestock farming. Conclusions Changes in pastoral farming practices are likely to account for at least some of the decline in the wider countryside, probably related to changes in food resources, though these are largely unquantified.

Chaffinch Fringilla coelebs foraging patterns, nestling survival and territory distribution on lowland farmland

Numbers of many bird species which breed on farmland, and are reliant on cropped land for feeding or nesting, declined between the 1960s and 1990s. In contrast, Chaffinch Fringilla coelebs numbers increased on farmland over the same period. This study investigates the influence of both cropped and non-cropped land on Chaffinches foraging for nestlings, nestling survival and territory density. The study was carried out on nine mixed lowland farms in south central England in 1996 and 1997. Chaffinches made little use of cropped areas when foraging for young (less than 9% of foraging visits, despite cropped areas covering 93% of study areas). Instead, trees and bushes influenced foraging patterns and breeding success. Extensive use was made of trees and bushes by adults searching for food for nestlings (75% of foraging visits were to hedges and trees within boundaries or fields, despite these areas covering <3% of study areas). Oaks (69% of visits) and Willows (15% of visits) were found to be the most favoured species of tree for foraging. In one year of the study, chick starvation was less frequent in nests located on field boundaries with Oak trees than in nests on boundaries without Oaks. Successful nests also tended to be closer to Oak or Willow trees than those where nestlings starved. Territory density was not related to hedgerow structure, presence or absence of Oaks and Willows in field boundaries, or adjacent cropping. Our findings on nest survival were supported by analysis of British Trust for Ornithology nest record data which revealed that nests associated with trees had better brood survival rates than sites not located close to trees. The use of trees and shrubs for feeding and nesting in the farming landscape and the ability to utilize unkempt hedgerows may have contributed to the ability of Chaffinches to persist on farmland despite wide-scale agricultural change in recent decades.

Agricultural habitat-type and the breeding performance of granivorous farmland birds in Britain.

Conservation concern about granivorous birds has led to the implication of changing agricultural practices as causes of widespread population decline. We investigate relationships between breeding performance and the agricultural environment for ten granivorous farmland bird species (Stock Dove Columba oenas, Skylark Alauda arvensis, Tree Sparrow Passer montanus, Chaffinch Fringilla coelebs, Greenfinch Carduelis chloris, Linnet C. cannabina, Bullfinch Pyrrhula pyrrhula, Reed Bunting Emberiza schoeniclus, Yellowhammer E. citrinella and Corn Bunting Miliaria calandra). We analyse long-term, extensive data from the British Trust for Ornithologys Nest Record Scheme on breeding performance per breeding attempt with respect to farmland type (arable, grazing or mixed) and time (pre- and post-1975–76). The influence of habitat is investigated at two different scales: within the nesting territory and at the landscape level. Relationships between farmland type and (temporal changes in) breeding performance tended to be species-specific, but a few patterns were each common to some species. Improvements in breeding performance occurred across all three farmland types for four declining species. Grazing farmland seems to have deteriorated as breeding habitat for Linnet and arable/mixed farmland for Reed Bunting. Mixed farming at the territory scale supported better breeding performance for four species, three of which (Bullfinch, Yellowhammer and Corn Bunting) have declined concurrently with mixed farming. Pastoral landscapes supported better breeding performance for up to seven species, six of which have undergone large declines. Arable landscapes supported better breeding only for the stable or increasing Chaffinch and Greenfinch. Different relationships between farming regime and breeding performance were found at the two scales considered.

The decline of the Bullfinch Pyrrhula pyrrhula in Britain: is the mechanism known?

Abstract. The Bullfinch has declined in Britain and elsewhere in Europe, but definitive evidence about the cause and demographic mechanism has yet to be published. We review current knowledge, concentrating on analyses of demography, and present new integrated population modelling analyses designed to reveal the demographic changes most important in the decline. It is likely that changes in brood size and clutch size have not been important and our models suggest that the decline can be explained without invoking variation in numbers of breeding attempts or post-fledging survival rates. However, although changes in the egg period daily nest failure rate provide the best explanation for population change during the years of steepest decline, nestling period failures, adult survival and first-year survival could all have been equally important. Egg period nest failure rates have been higher in the preferred habitat, woodland, than in farmland and have fallen over time in farmland, where a larger decline has occurred (65 % versus 28% ), arguing against a causal link with abundance. Despite evidence for a negative effect of agricultural intensification on Bullfinch presence, little evidence exists clearly linking any demographic rate to environmental change and agricultural land-use has had little effect on nest failure rates. Predation appears to have had no significant impact. Future work should focus on contemporary investigations of the importance of hedgerow structure and woodland understorey vegetation.

Possible roles of habitat, competition and avian nest predation in the decline of the Willow Tit Parus montanus in Britain

Capsule Although stable in their preferred, wet habitats, Willow Tits have declined in woodland, probably because of habitat degradation rather than increases in avian nest predator and competitor numbers. Aims To elucidate the cause of the population decline by investigating variations with habitat and testing the hypothesis that an increase in nest predators or competitors (especially for nest-holes) could be responsible. Methods I analysed with respect to survey plot habitat over 30 years of Willow Tit abundance data from a national survey. I examined the relationships with the local abundance of key potential nest predators (woodpeckers and Jay Garrulus glandarius) and key potential competitors (other tit species and Nuthatch Sitta europaea). Results Willow Tits have declined in farmland and woodland in Britain, but not in their preferred, wet habitats. There was no evidence for any negative effect of competition and the only potentially important negative correlation with the abundance of a predator (Great Spotted Woodpecker Dendrocopus major) was limited to farmland, a relatively minor habitat. A negative relationship with Green Woodpecker Picus viridis probably reflects opposite habitat preferences. Conclusions Although correlative studies of competition and predation cannot be definitive, the evidence of this study suggests that the major cause of the Willow Tits decline in Britain is habitat degradation, especially in woodland. Possible mechanisms for this degradation are discussed.