Guy Q.A. Anderson

Agriculture: Widespread local house-sparrow extinctions

House-sparrow populations have declined sharply in Western Europe in recent decades, but the reasons for this decline have yet to be identified, despite intense public interest in the matter. Here we use a combination of field experimentation, genetic analysis and demographic data to show that a reduction in winter food supply caused by agricultural intensification is probably the principal explanation for the widespread local extinctions of rural house-sparrow populations in southern England. We show that farmland populations exhibit fine-level genetic structuring and that some populations are unable to sustain themselves (sinks), whereas others act as sources.

Widespread local house-sparrow extinctions

House-sparrow populations have declined sharply in Western Europe in recent decades, but the reasons for this decline have yet to be identified, despite intense public interest in the matter. Here we use a combination of field experimentation, genetic analysis and demographic data to show that a reduction in winter food supply caused by agricultural intensification is probably the principal explanation for the widespread local extinctions of rural house-sparrow populations in southern England. We show that farmland populations exhibit fine-level genetic structuring and that some populations are unable to sustain themselves (sinks), whereas others act as sources.

Foraging habitat selection, diet and nestling condition in Yellow Wagtails Motacilla flava breeding on arable farmland

Capsule Yellow Wagtails showed seasonally variable foraging preferences, favouring field margin and crop habitats, although habitat availability did not influence brood productivity. Aims To identify key habitats and prey types for Yellow Wagtails in arable farmland, assessing the importance of foraging habitat availability in determining breeding productivity. Methods Intensive nest searches were conducted across six areas in eastern England over two breeding seasons. Focal nest watches were used to determine foraging habitat selection. Nestling condition was analyzed in relation to surrounding habitat characteristics and weather conditions. Diet was assessed using chick faecal samples. Results Wet ditches and tracks were favoured foraging habitats, together with crop fields used for nesting. Crop preference varied seasonally, with autumn‐sown wheat preferred in May–June and potatoes preferred in July–August. Chick diet was dominated by flies (Diptera), although beetles (Coleoptera) were prevalent in early broods and damselflies (Zygoptera) in late broods. Weather and foraging habitat availability were poor predictors of nestling condition. Conclusion Our results highlight key microhabitats for Yellow Wagtails in arable farmland. The late‐season avoidance of autumn‐sown cereals implies that breeding season length could be limited in cereal‐dominated areas. The provision of alternative late‐season breeding habitats might represent an effective conservation strategy for this species.

Bird use of cultivated fallow ‘Lapwing plots’ within English agri‐environment schemes

Capsule Northern Lapwings Vanellus vanellus occurred on about 40% of fallow plot options within agri‐environment schemes; this could be increased by improved management and better placement of plots in the landscape. Aims To determine the use by Lapwings (and other species) of fallow plot options from the UK Countryside Stewardship and Higher Level Stewardship (HLS) agri‐environment options. Methods The number of Lapwings and other bird species using a plot and any evidence of breeding by Lapwings was recorded. Adjacent crop and boundary features, and vegetation height and bare ground within the plot, were recorded. Results Approximately 40% of the 212 plots surveyed were used by Lapwings. Breeding was suspected on 25% of plots and was proven on 11%. Lapwing presence was lower where woodland was close to the plot and breeding evidence was more likely on plots with more bare ground. Sky Larks Alauda arvensis, Woodpigeons Columba palumbus and Yellowhammers Emberiza citrinella were also frequently recorded. Conclusions Fallow plot options are one of the most expensive per‐hectare agri‐environment options under HLS. Better ‘value for money’ could be achieved by ensuring that a greater proportion of plots are (1) managed to promote a short broken sward, with plenty of bare ground; and (2) placed in open landscapes away from woods and vertical features.

Land-use correlates of breeding performance and diet in Tree Sparrows Passer montanus

Capsule Chick diet varies seasonally and between wet and dry habitats, and there is little evidence for a link between habitat type and productivity. Aim To examine the influence of habitat composition and diversity on Tree Sparrow productivity and nestling diet in a wide variety of locations across the UK. Methods Productivity, chick diet and habitat data were collected from Tree Sparrow nestbox colonies by volunteer bird-ringers in 2002. Nestling diet was assessed by identification of invertebrate remains in faecal sacs. Results Clutch size was significantly higher for Tree Sparrows breeding in farmland than for those in wetland colonies. This did not translate into increased productivity. There was no other evidence of any effect of habitat or nestling diet composition on annual productivity. Diet composition varied seasonally, with habitat type and between individual sites. Conclusions Tree sparrows are capable of successful breeding in a range of habitats, where they utilize a wide range of invertebrate prey types. Lack of evidence for a relationship between habitat composition and productivity within this study may be the result of Tree Sparrows on farmland being restricted to areas providing adequate invertebrate food resources. To reduce the probability of Tree Sparrow populations on farmland being limited by chick food invertebrates, conservation measures aimed at population recovery should include the provision of habitats to support a range of high value invertebrate taxa throughout the protracted breeding season. Mechanisms to provide such habitats are already available within existing UK agri-environment schemes.

Effects of agri-environment management for cirl buntings on other biodiversity

Agri-environment scheme (AES) management has increased populations of cirl buntings (Emberiza cirlus) in South Devon, England, and might be expected to provide benefits for other declining biodiversity, due to less intensive farm management. Fields managed under AES for cirl buntings (low-input spring barley or permanent pasture without inputs) were contrasted with control fields under conventional management (spring barley without management restrictions and winter cereals, or grazed without management restrictions) to identify such benefits for vascular plants, butterflies, bumblebees, carabid beetles, foliar invertebrates and bats. Activity-density and species richness of carabid beetles were both higher in AES spring barley fields than in control spring barley and winter cereal fields. Forb cover and abundance of butterflies and bumblebees were higher in AES spring barley fields than in winter cereals, but did not differ between AES and control spring barley. No difference was observed in plant species richness between any of the arable field types. Plant species richness and butterfly abundance were higher in AES pasture fields than in controls. Abundance, activity-density and/or species richness of other taxa did not differ between AES and control pastures. Benefits observed in AES spring barley fields arise from management specific to AES agreements, and also, we suggest, from the maintenance of spring-sown barley in the landscape. Benefits in AES pasture fields are ascribed to the absence of fertiliser and pesticide inputs, and reductions in stocking arising from this; there is also likely to have been some pre-selection for older pastures to be entered into AES management agreements. Agri-environment measures for cirl buntings have benefits for a range of taxa beyond the target species, and therefore, largely through reduction of management intensity and maintenance of land-use diversity, improve the overall biodiversity of the farmed landscape where they are present.

Breeding ecology of Yellow Wagtails Motacilla flava in an arable landscape dominated by autumn-sown crops

Capsule Yellow Wagtails successfully raised two consecutive broods in landscapes dominated by autumn-sown crops and did not require spring crops or fallow plots for later nesting. Aims To assess whether arable landscapes dominated by winter cropping provide habitats that allow Yellow Wagtails to raise two successful broods. To assess the utility of spring cultivated agri-environment fallow plots as a nesting and foraging habitat for Yellow Wagtails. Methods Nesting success and foraging behaviour of Yellow Wagtails was monitored on lowland arable farmland dominated by winter cropping during two successive breeding seasons. Results Yellow Wagtails successfully raised first and second broods mainly in winter cereals, with later nests being more successful. Some nests were initiated in bean fields where egg-stage failure rates were high, probably as a consequence of depredation. Fallow plots were not used for nesting but, along with other areas of sparse vegetation, were regularly used for foraging. Conclusions Yellow Wagtails breeding at relatively low densities achieved high rates of reproductive success in a landscape dominated by winter cereals and with few spring-sown crops. This study suggests that spring-sown crops may not be necessary for Yellow Wagtails to rear two successful broods each summer within arable landscapes.

Bird use of establishment-stage Miscanthus biomass crops during the breeding season in England

Capsule Summer bird densities in establishment-stage (2–3-year-old) Miscanthus were the same as in winter wheat fields for many species, but were higher for Lapwing, and for Reed Bunting and Blackbird late in the summer. Aims To compare abundances of farmland birds in establishment-stage Miscanthus biomass crops with those in crop types they are likely to replace (winter wheat and grassland) during the breeding season. In particular, to investigate whether such a rapid-growing, dense crop has lower abundances of field-nesting species. Methods Bird surveys were conducted in 51 Miscanthus fields and an equal number of grass or winter wheat control fields between May and July, in Lincolnshire and southwest England. Results Species richness was similar in Miscanthus to that in winter wheat and grass. Skylark densities were similar in Miscanthus and wheat, while Lapwing densities were higher in Miscanthus and grass than wheat. Miscanthus contained very high densities of Reed Buntings and Blackbirds late in the summer. Conclusion Densities of most bird species, including field-nesting species, were not lower in establishment-stage Miscanthus than in the crops it most commonly replaced. The Miscanthus surveyed was relatively weedy and patchy; further studies as crops age and knowledge of Miscanthus husbandry increases would be valuable.

Widespread local house-sparrow extinctions: Agriculture

House-sparrow populations have declined sharply in Western Europe in recent decades, but the reasons for this decline have yet to be identified, despite intense public interest in the matter. Here we use a combination of field experimentation, genetic analysis and demographic data to show that a reduction in winter food supply caused by agricultural intensification is probably the principal explanation for the widespread local extinctions of rural house-sparrow populations in southern England. We show that farmland populations exhibit fine-level genetic structuring and that some populations are unable to sustain themselves (sinks), whereas others act as sources.