1. Although climate is known to play an important role in structuring biological communities, high-resolution analyses of recent climatic impacts on multiple components of diversity are still sparse. Additionally, there is a lack of knowledge about which species drive community response to environmental change. 2. We used a long-term breeding bird data set that encompasses a large latitudinal and altitudinal range to model the effect of temperature on spatial and temporal patterns in alpha and beta diversity. We also established a novel framework for identifying species-specific contributions to these macroecological patterns, hence combining two different approaches for identifying climatic impacts. 3. Alpha diversity increased over time, whilst beta diversity declined; both diversity metrics showed a significant relationship with recent temperature anomalies. By partitioning beta diversity, we showed that the decline was predominately driven by changes in species turnover rather than nestedness suggesting a process of replacement by more common species. 4. Using jackknife analyses we identified how individual species influenced the modelled relationships of diversity with temperature and time. Influential species tended to be habitat generalists with moderate to large distributions. 5. We demonstrate that different facets of avian diversity can respond rapidly to temperature anomalies and as a result have undergone significant changes in the last decade. In general, it appears that warming temperatures are driving compositional homogenization of temperate bird communities via range expansion of common generalist species.

Aims Biogeographical evidence suggests a strong link between climate and patterns of species diversity, and climate change is known to cause range shifts. However, there is little understanding of how shifts affect community composition and we lack empirical evidence of recent impacts of climate change on the diversity of vertebrates. Using a long-term comprehensive dataset on bird abundance, we explore recent patterns of change in different components of species diversity and avian communities, and postulate a process to explain the observed changes in diversity and specialization.Location Britain.Methods We used Breeding Bird Survey data for Britain from 1994 to 2006 to calculate site-specific diversity and community specialization indices. We modelled these indices using generalized additive models to examine the relationship between local climate and spatial and temporal trends in community metrics and the relationship between changes in diversity and specialization.Results Local temperature was positively associated with alpha diversity, which increased over the study period, supporting empirical and theoretical predictions of the effect of climate warming. Diversity increased in all habitats, but the rate of increase was greatest in upland areas. However, temperature was negatively associated with community specialization indices, which declined over the same period. Our modelling revealed a nonlinear relationship between community specialization and species diversity.Main conclusions Our models of diversity and specialization provide stark empirical evidence for a link between warming climate and community homogenization. Over a 13-year period of warming temperatures, diversity indices increased while average community specialization decreased. We suggest that the observed diversity increases were most likely driven by range expansion of generalist species and that future warming is likely to increase homogenization of community structure. When assessed in combination, diversity and specialization measures provide a powerful index for monitoring the impacts of climate change.

The Entry Level Stewardship scheme, introduced in 2005, is the first non-competitive, broad-uptake scheme designed to deliver simple but effective environmental management on farms throughout England. While previous analysis suggests that the benefits of the scheme at the national scale may be limited thus far, efficacy may vary on a regional basis because of spatial differences in the uptake of individual options, in local environmental resource gaps or in the population status of key species. We assessed the influence of Entry Level Stewardship on regional population changes between 2005 and 2008 of farmland bird species. Trends were derived from standardised surveys carried out across eight geographical regions in England in more than 2000 lowland farmland 1 km squares. Birds showed apparent region-specific population trends and responses to Stewardship options. Boundary management had a positive association with the population trends of several species in both Yorkshire and the North West. Neither grass field margins nor the provision of winter foraging resources appeared to have any substantial benefits across any regions. An important influence of regional context was suggested by contrasting effect of management on some species, such as linnet, across regions. This study suggests that there are regional differences in the efficacy of options and responses of bird populations, although the number of tests conducted means that some of the apparent results may represent statistical artefacts. Nevertheless, this study suggests that agri-environment schemes like Entry Level Stewardship would be improved by greater consideration of regionality in biodiversity responses and efficacy than is currently common in standard schemes. (C) 2010 Elsevier B.V. All rights reserved.

Agri-environment schemes (AES) are central to the conservation of Europe's farmland biodiversity. The UK Government's Public Service Agreement target seeks to reverse the decline of farmland birds in England by 2020 through the use of AES. The Entry Level Stewardship (ELS) scheme, introduced in 2005, is the first non-competitive, broad-uptake stewardship scheme designed to deliver simple but effective environmental management on farms throughout England. Approximately 5 million hectares of farmland are currently entered into Environmental Stewardship (ES) agreements, and given the scale of this investment it is important to verify the efficacy of ELS as a mechanism for delivering biodiversity benefits. We used spatially referenced ES agreement data to assess the influence of specific management options and combinations of options on farmland bird population changes between 2005 and 2008 derived from standardized surveys carried out on over 2000 lowland farmland 1-km squares in England. The results showed only limited evidence for short-term effects of ES. Only Corn Bunting Emberiza calandra and Common Starling Sturnus vulgaris showed some landscape-specific positive associations with area under ELS management. There was also limited evidence for positive associations between specific management options and the population changes of the species at which they were aimed. The current pattern of option uptake may be limiting benefits of ELS, with boundary management accounting for over 50% of scheme compensation value. However, the time required for option maturation and the time lags in bird population responses to environmental change mean that it is too early to reach definitive conclusions about the success or failure of the scheme. The findings of this study will assist in the development of ELS by feeding into the 5-year review scheduled for 2010 and have implications for the development of similar schemes elsewhere in Europe.

Capsule Hedgerows and margins managed under agri‐environment schemes appear to attract greater numbers of some farmland bird species. Aims To examine fine‐scale habitat associations of farmland birds to determine whether Entry Level Stewardship, the wider countryside agri‐environment scheme for England, provides a mechanism for affecting population changes. Methods Ninety‐seven 1‐km squares in East Anglia were surveyed to create two‐dimensional habitat maps showing the location of all habitat patches and associated stewardship management. Modified territory‐mapping techniques were used to produce relative estimates of bird numbers within each discrete habitat patch within each square. The effect of Entry Level Stewardship on species density was then analysed using glms. Results Boundaries managed under Entry Level Stewardship appeared to attract higher densities of Blue Tits, Dunnocks, Common Whitethroats and Yellowhammers. Margins managed under the scheme also had higher densities of Yellowhammers. Conclusions Existing boundary habitat management under Entry Level Stewardship may provide a mechanism for increasing the populations of some farmland bird species. Boundary management options should continue to be promoted, although rebalancing the scheme more towards in‐field options is likely to be more widely beneficial.