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Summary1. Set-aside is arable land rested from normal intensive operations, usually providing, in summer, a relatively sparse, weedy or grass-dominated sward without pesticide or fertilizer inputs. Set-aside is therefore potentially attractive to breeding and foraging birds and is predicted to contribute to increased avian biodiversity on arable or mixed farmland. Set-aside mimics low intensity farmland within the heart of the industrial farm landscape, thereby allowing direct comparison with intensive crops regarding their respective values for the bird fauna. 2. In this study, bird abundance was compared between set-aside and nearby crops or grassland. A particular focus of the study was to identify the breadth or generality of any preferences across a suite of farmland species, using data from a broad representation of English farms. Thus, an extensive survey of birds utilizing ®elds, including set-aside, was conducted on 92 arable farms in England during 1996 and 1997. Each farm was visited four times in each summer, habitat details were recorded, and all birds seen or heard were mapped using a standard technique. 3. Field type preferences were examined across bird functional groups representing gamebirds, pigeons, crows, skylark Alauda arvensis, thrushes (Turdidae) and granivorous passerines (Passeridae, Fringillidae and Emberizidae). The relationship between bird abundance and ®eld type was analysed using log-linear Poisson regression and compositional analysis. 4. Both analyses revealed that bird abundances were signi®cantly higher on setaside than on winter cereals for all six functional groups, and were highest on rotational set-aside for all functional groups except crows (which preferred grassland). Winter cereals or grassland were generally the least preferred habitat. 5. On farms where both rotational and non-rotational set-aside was present, preferences were strongest for rotational set-aside for all functional groups except crows (which preferred non-rotational set-aside). This underlines the dierences between set-aside sward composition in in¯uencing bird numbers. 6. The results show broad-scale preferences for set-aside over crops or grassland for species representing non-passerines, passerines, insectivores and granivores, for a wide representation of farms in England. For the majority of species, this preference implies that set-aside is utilized as a source of food, and the scale of this preference is impressive given that most set-aside was not managed speci®cally for bird conservation. However, not all types of set-aside were equally exploited by birds, as the strongest preferences were for natural regeneration rotational set-aside rather than the more structurally uniform non-rotational set-aside. 7. The results are important in the context of the potential loss of set-aside from the arable countryside, but also for the development of future agri-environmental schemes. We suggest that, to reverse population declines of many farmland birds in Britain, such schemes will need to be introduced...

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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.