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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.

and { RSPB, The Lodge, Sandy, Bedfordshire SG19 2 DL, UK Summary 1. Yellowhammers began to decline on British lowland farmland in the late 1980s and losses are presently 10% per year. This study examined variation in the habitat selection and breeding success of yellowhammers, allowing an evaluation of whether Britain's yellowhammer decline might have been caused by recent changes in agriculture. 2. Yellowhammer territories were associated with hedgerows, vegetated ditches and wide uncultivated grassy margins around ®elds. Pasture and silage leys were avoided. Nests were built among herbaceous vegetation in ditches or in the shrubby vegetation of hedgerows. 3. Breeding started slightly earlier on organic farms than on intensively managed farms, but no measure of breeding success diered between farm types. Predation was the cause of most (64%) nest failures. A maximum of three breeding attempts (two successful) was observed per pair, with a mean clutch size of 3Á3, a May®eld nest success rate of 0Á46, and 2Á6 nestlings¯edged per successful brood. These data, together with published estimates of adult yellowhammer survival and of post-¯ed-ging survival among other passerines, suggest that breeding productivity is too low to maintain a stable population. 4. The removal of hedgerows or abandonment of hedge management, ®lling or clearing of ditches, intensi®cation of grassland management and cropping or grazing right up to the ®eld edge, are all likely to have adversely aected yellowhammers on lowland farmland in southern England. Policy reforms that redirect subsidy support to environmentally bene®cial management of ®eld margin habitats and retention of winter-feeding sites such as stubbles should assist in restoring populations of breeding yellowhammers on lowland farmland. 5. Our data expand further the array of farmland bird species for which interactions between agricultural change and population change are increasingly understood.

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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.

SUMMARY 25Trichomonas gallinae is an emerging pathogen in wild birds, linked to recent 26 declines in finch (Fringillidae) populations across Europe. Globally, the main 27 hosts for this parasite are species of columbiformes (doves and pigeons); here 28 we carry out the first investigation into the presence and incidence of 29Trichomonas in four species of columbiformes in the UK, through live sampling of 30 wild-caught birds and subsequent PCR. We report the first known UK cases of 31

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 wintercereal-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.