Landscape-dependent use of a seed-rich habitat by farmland passerines: relative importance of game cover crops in a grassland versus an arable region of Scotland

Capsule Game cover crops in a pastoral region of southwest Scotland supported passerines at more than twice the density found in similar crops in an arable region.

Aims To investigate the use of seed-rich habitats (game cover crops) by farmland passerines in the agricultural grasslands of southwest Scotland relative to the arable east.

Methods Birds were counted in game cover crops and conventional crops on nine farms in Dumfries and Galloway, and Ayrshire, during the winters of 2003/04 and 2004/05. Similar data from eastern Scotland were re-analysed to compare the relative use of the two crop types in the contrasting regions.

Results Passerine densities in game cover crops in southwest Scotland were two orders of magnitude greater than in conventional crops. Furthermore, densities within grassland game cover crops were more than double those in arable areas and densities in grassland conventional crops were just 14% of those in equivalent arable habitats.

Conclusion The significantly greater difference between passerine densities in game cover crops and conventional crops in a grassland versus an arable region of Scotland could not be explained by differences in the bird communities, crop types, boundary habitats, weather, observer effects or survey methods used. We suggest that game cover crops may be more attractive in grassland regions because alternative food sources are rarer than in arable regions.     

Songbirds using crops planted on farmland as cover for game birds

We counted songbirds in crops planted on shooting estates specifically for game management purposes on farmland in Britain and elsewhere in Europe. Winter game crops provide cover and feed areas for pheasants Phasianus colchicus and red-legged partridge Alectoris rufa, while summer game crops are designed to provide brood-rearing cover for these species. In central and southern England, 30 plots of winter game crops, either kale, quinoa or cereal up to 2 ha in area, and 30 adjacent arable-field plots, were surveyed for birds up to six times at monthly intervals during the winter 1997–1998. In the Scottish lowlands, six plots of summer game crops up to 4 ha in area, and adjacent arable fields were surveyed in summer 1999 or 2000. The winter game plots contained more than ten songbirds per hectare in most months, while the adjacent arable-field plots contained less than one. In all three winter game crop types, songbird numbers declined significantly in the second half of the winter while numbers in the arable fields did not. Of the 26 species recorded in the winter game crops, 10 have undergone rapid decline over the last 30 years. Considering these declining species alone, the winter game crops still contained more individuals than the adjacent arable fields throughout the winter. Densities in both the kale and quinoa were higher than in the cereal game crop. The six summer game crops sampled in mid-summer contained on average 2.9 songbirds per hectare, while the adjacent arable fields contained 0.4. Of the 14 species recorded in these summer game crops, eight have undergone rapid or moderate declines over the last 30 years. Although winter and summer game crops are planted in relatively small plots and hence concentrate birds, these plots are widely planted and our results suggest that they benefit birds on farmland.     

Development of an agri-environment scheme option: seed-bearing crops for farmland birds

Winter mortality, resulting from reduced food supply during a period of agricultural intensification, is thought to have driven population declines for some farmland bird species. Planting of game crops has increased over this period in order to provide food and cover for gamebirds. We investigate the potential of this managed habitat for farmland songbird conservation, using intensive single-site studies, and an extensive national survey. Game crops were used more than other farmland habitats by a wide range of bird species. Kale and quinoa were used by many species, whereas maize was used by very few. Cereals such as triticale and millet were used by many species, including several not associated with brassicas such as kale. Crop species differed in the rate of seed shedding, and therefore in the amount of seed food that they provided through the winter. Crop location influenced use by some bird species, with crops close to hedges or other cover generally being favoured. Use of nitrogen fertilizer influenced seed yield, and therefore crop value as a source of food for birds. Our results suggest that, if managed and sited correctly, a combination of two or three crop species can provide a valuable winter food resource for many nationally declining farmland bird species, but further attention needs to be given to their agronomy. This form of management is now incorporated as an option within agri-environment schemes in England, Scotland and Wales. It enables farmers to apply existing skills to conservation and is compatible with their cultural values.     

Winter habitat associations of seed-eating passerines on Scottish farmland

CapsuleExtensive surveys highlighted the importance of weedy fodder brassicas, stubbles and open farmland landscapes to declining birds.

Aims To determine habitat associations of seed-eating passerines on Scottish farmland in winter, and recommend appropriate conservation measures.

Methods Transect surveys were carried out on farmland in 100 1-km squares, containing 2885 fields, across Scotland. Birds, crops, field boundary features and weeds were recorded on three visits. Bird–habitat associations were examined using logistic regression models.

Results Seed-eating passerines were highly concentrated: 100 fields (1.4% of the area surveyed) held half the total count. The highest field densities of birds were recorded in fodder brassica crops and stubbles, averaging 12 and 3.3 birds/ha respectively. In fodder crops, weedier fields held many more birds. Multiple regression analysis emphasized the importance of fodder crops, stubbles and farmyards and suggested that declining bird species preferred more open landscapes. Several bird species were associated with fields containing very weedy patches, and/or weeds of the family Chenopodiaceae. These features were commonest in fodder brassicas. Many of the crop types found to be important as bird habitats in winter have declined in area in Scotland; the availability of seed food in such habitats may also have diminished. Such changes may partly explain recent population declines.

Conclusions Agri-environment measures for seed-eating passerines should support the widespread provision of small areas of seed-rich wintering habitats, such as weedy fodder brassicas and stubbles, especially in open (0–10% woodland and scrub) landscapes in areas with mild winters.     

Mate guarding in the Linnet Carduelis cannabina

Capsule?House Sparrow (Passer domesticus) populations in south Swedish farmland are not affected by supplemental winter feeding, irrespective of agricultural landscape type or presence of animal husbandry, although winter populations declined more in mixed farmland and when farms contained animal husbandry.

Aims?To investigate whether food limitation of House Sparrow population size during the winter varied spatially in relation to agricultural landscape intensification and farm management.

Methods?We experimentally increased the winter food supply for populations on farmsteads in replicated landscapes that differed in agricultural intensification (open plains versus mixed farming) and/or farm management (crop farming versus animal husbandry), and estimated possible differences in effects on winter population change.

Results?We found no effect of supplementary winter feeding on changes in House Sparrow population sizes over the winter, irrespective of agricultural landscape type or presence of animal husbandry at the farm. However, we found a significantly larger winter population decline in mixed farmland and when farms contained animal husbandry.

Conclusions?The results suggest that House Sparrow populations in south Swedish farmland are not primarily limited by winter food availability. Alternatively, supplemental winter feeding may augment interspecific competition or attracts predators, offsetting any positive effect on population change. However, the stronger population decline in landscapes in which more breeding resources may be available (animal husbandry farms, mixed farmland), suggests stronger intraspecific competition during the winter in line with the resource separation hypothesis.     

Winter use of wild bird cover crops by passerines on farmland in northeast England

Capsule Declining farmland species were more abundant in these crops which can be matched to the birds' requirements.

Aims To assess the use of seed-bearing crop by a range of bird species in winter.

Methods The study was carried out over three winters at a site in County Durham (England). Eleven bird species were represented, five of which are nationally targeted for conservation action.

Results Bird abundance was significantly higher where wild bird cover crops were present. Kale Brassica napus and Quinoa Chenopodium quinoa were the most used crop species, although cereals and linseed were also used.

Conclusion Simple crop mixtures can be designed to meet the needs of farmland bird communities. Our results suggest that seed production may be limited within government agri-environment schemes by restrictions on fertilizer use. The agronomy of seed-bearing crops for birds requires further investigation.     

The provision of winter bird food by the English Environmental Stewardship scheme

Environmental Stewardship (ES) is the main mechanism for reversing the decline in farmland birds in England, and includes a range of options designed to provide winter foraging for seed‐eating species. We estimated granivorous songbird densities on ES options designed to provide winter food, on farms within the Entry Level (ELS) or Higher Level (HLS) strata of ES. ES Wild Bird Mixtures (WBMs) hosted higher densities and a wider range of granivores than non‐ES game covers, although in East Anglia the enhanced HLS WBM was used no more than the basic ELS WBM. In the West Midlands there were low densities of granivores on all WBMs and game covers. The widespread ELS WBM appeared to provide little food for buntings but supported finches, partially through greater weed burdens. There was a weak, non‐significant trend for Skylarks Alauda arvensis to make greater use of ELS cereal stubbles than non‐ES stubbles, possibly because of post‐harvest herbicide restrictions allowing overwinter weed growth. At the field scale, this work demonstrates that although some ES options provide winter food resources for birds, there is limited evidence for additional benefits of Higher Level vs. Entry Level Stewardship to wintering farmland songbirds.     

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.     

Weed seed resources for birds in fields with contrasting conventional and genetically modified herbicide-tolerant crops

The UK Farm Scale Evaluations (FSEs) have shown that the use of broad spectrum herbicides on genetically modified herbicide-tolerant (GMHT) crops can have dramatic effects on weed seed production compared to management of conventional varieties. Here, we use FSE data and information on bird diets to determine how GMHT cropping might change the food resources available to farmland birds. More than 60 fields of each of four crops, spring- and winter-sown oilseed rape, beet and maize, were split, one half being sown with a conventional variety, the other with a GMHT variety. Seed rain from weeds known to be important in the diets of 17 granivorous farmland bird species was measured under the two treatments. In beet and spring oilseed rape, rain of weed seeds important in the diets of 16 bird species was significantly reduced in GMHT compared to conventional halves; for no species did it increase. In winter oilseed rape, rain of weed seeds important in the diets of 10 species was significantly reduced in GMHT halves; for only one species did it increase significantly. By contrast, in maize, rain of weed seeds important in the diets of seven species was significantly greater in GMHT halves; for no species was it reduced. Treatment effects for the total weed seed energy available to each bird species were very similar to those for seed rain alone. Measuring the effects on individual bird species was outside the scope of this study. Despite this, these results suggest that should beet, spring and winter rape crops in the UK be largely replaced by GMHT varieties and managed as in the FSEs, this would markedly reduce important food resources for farmland birds, many of which declined during the last quarter of the twentieth century. By contrast, GMHT maize would be beneficial to farmland birds.     

Density and productivity of breeding Skylarks Alauda arvensis in relation to crop type on agricultural lands in western France

Capsule Small field size and the maintenance of set-aside and lucerne are important to ensure high breeding pair densities and productivity.

Aims To investigate the effects of crop types and their attributes on density and productivity of breeding Skylark.

Methods At each of four selected study sites in western France, territory density, vegetation height, vegetation cover and field size was estimated by field and attempts were made to find nests. Crop types included winter and spring cereals, oilseed rape, sunflower, maize, grass, lucerne, set-aside, and bare ground.

Results About 80% of Skylark territories included more than one crop type. Birds preferred small fields and territory density decreased with increasing field size. Density was highest in crops with low vegetation height and cover. Set-aside, lucerne and grass supported highest territory density. Fledging productivity was highest in set-aside and lucerne, and was zero on bare ground. Skylark density decreased throughout the breeding season (-26% in 1999 and -29% in 2000), suggesting an instability in territory distribution or activity in intensive farmland.

Conclusions Farming systems that decrease field size and increase set-aside and lucerne instead of oilseed rape, maize and sunflower will benefit Skylark and other declining farmland species.     

The effects of habitat and spatial features of wetland fragments on the abundance of two rallid species with different degrees of habitat specialization

The management of wild gamebirds for shooting involves a combination of habitat management (woodland, field boundaries and game crops), winter feeding and control of potential nest predators, any of which could benefit other birds, including nationally declining species associated with farmland habitats. Changes in numbers of passerines were monitored over six years in relation to game management on farmland in Leicestershire. Nest success was monitored over four years and, for some species, was inversely related to abundance of breeding corvids. Abundance of breeding passerines increased during the period of game management. Species whose breeding populations have declined nationally (coincident with agricultural intensification) showed the greatest increases in abundance relative both to other species, and to the same nationally declining species in nearby farmland. The precise mechanism by which the game management package contributes to increased breeding numbers is not understood and is likely to differ between species. However, these results show that further integration of wild game management into farming systems could have conservation benefits for nationally declining farmland birds.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Non-inversion tillage and farmland birds: a review with special reference to the UK and Europe

This paper reviews the current knowledge of the effects of non-inversion tillage (NIT) on farmland birds and their food resources. NIT is a method of establishing a crop without using a mouldboard plough and is becoming increasingly popular in the UK. NIT generally disturbs the soil to shallower depths than conventional tillage and is therefore expected to have beneficial effects on biodiversity on arable land as compared with mouldboard ploughing. The diets of farmland birds change throughout the year, and many species take invertebrates over the breeding season. Seeds are also important for many species of farmland birds throughout the year and especially over the winter months. The effects of NIT on these farmland bird food resources, in particular ground beetles (Coleoptera: Carabidae), spiders (Arachnida: Araneae), earthworms (Annelida) and seeds (arable weeds and cereal crops) are reviewed.     

Variations in Black Grouse Tetrao tetrix winter survival in a year with prolonged snow cover

Capsule Low Black Grouse survival rate in northern England during a severe winter with prolonged snow was attributed to limited availability and proximity of woodland.

Aims To compare the impact of the severe winter weather on Black Grouse in an open treeless landscape in northern England with more wooded landscapes in Scotland.

Methods We assessed the impact of severe winter conditions in relation to previous milder winters at a sample of leks counted annually in northern England and the Scottish Highlands between 2001 and 2012. In addition, following the severe winter in 2009/10 Black Grouse were surveyed at all leks in 2010 where they were surveyed the previous year. We assessed woodland habitat extent within 1 km of leks and related this to indices of Black Grouse over-winter survival.

Results Black Grouse in northern England were severely affected by the severe winter of 2009/10, declining by 38% in comparison to a 23% increase in the Scottish Highlands. Leks in northern England were at higher altitudes and had less tree cover than those in Scotland.

Conclusion The lack of woodland cover around leks in northern England implies that availability of above snow forage, shelter and cover from predators was too low for Black Grouse to survive during prolonged deep snow. Measures are required to provide emergency food sources in periods of prolonged snow, such as the provision of supplementary food at leks, the cultivation of seed-rich arable crops, and the establishment of pockets of woodland.     

Habitat associations and breeding success of the Chaffinch Fringilla coelebs

Capsule Population trends for Chaffinch on farmland are unlikely to be explained by their preference for non-crop habitats alone.

Aims To investigate the importance of non-cropped habitats for Chaffinch territory distribution, breeding success and foraging habitat selection in Scottish farmland.

Methods Territory distribution, nesting success and foraging behaviour of adults feeding chicks at the nest were recorded and related to habitat composition on two Scottish lowland farms.

Results Higher Chaffinch territory densities were associated with the presence of hedgerows, trees and grass leys, whereas lower densities were found adjacent to winter Barley. Nests were predominantly located in conifer trees and hedgerows. Trees were selected preferentially for foraging. Poor breeding success was detected in nests associated with cereal crops and wider field margins. Farmland in Scotland supported much lower territory densities than in England.

Conclusion Chaffinches rely predominantly on non-cropped habitats for territory establishment, nesting and foraging habitats. Differences in habitat composition between England and Scotland may explain differences in territory densities. However, the Chaffinch's preference for non-crop habitats is unlikely to explain its population trends alone. Immigration from other habitats and/or a decrease in inter-specific competition for resources may also have contributed to the increase in the national farmland Chaffinch population.     

Distribution shifts in wintering Golden Plover Pluvialis apricaria and Lapwing Vanellus vanellus in Britain

Capsule The winter distribution of Golden Plover and Lapwing has shifted east since the mid-1980s, perhaps in response to climate change.

Aims To combine analyses of winter trends on wetlands and flocks on farmland to assess the current status of Golden Plover and Lapwing in one of their main wintering regions.

Methods Winter trends were derived from monthly counts on estuaries and wetlands for the period 1974–2002 (the Wetland Bird Survey). Winter distribution on farmland was assessed using casual records of large flocks and surveys of a stratified random sample of 1-km squares (the Winter Farmland Bird Survey).

Results Regional trends showed a pronounced increase in numbers of both species since 1974 on the east coast, with a smaller increase on the south coast. Numbers in the west and north tended to decline. Flocks on farmland were concentrated in eastern Britain unlike the situation in the 1980s.

Conclusions The winter distribution of Golden Plover and Lapwing has shifted to the east, resulting in large numbers on the east coast and in the arable east of Britain. The implications of this shift, especially in relation to known habitat associations, are discussed.     

Entry Level Stewardship may enhance bird numbers in boundary habitats

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.     

The past and future of farmland birds in Hungary

Capsule Populations of birds on farmland are larger and more stable in Hungary than in the UK and may provide baseline targets when planning population restoration programmes in more intensively farmed regions of Europe.

Aims To review the available evidence on farmland bird populations and their changes over the past century in Hungary, and to compare this with similar data for the UK.

Methods Published papers and grey literature were searched to determine long-term bird population trends for birds on farmland in Hungary, and for research evidence on the relationship between farmland management and bird diversity in Hungary.

Results Population density of common farmland birds is higher and trends are more positive in Hungary compared to the UK. These findings correlate with the recent change to generally less intensive agriculture in Hungary. However, while the birdlife associated with farmland in Hungary can be considered to have high diversity and density, it is still lower than it was in the first half of the 20th century and earlier. The few studies available showed that low-intensity traditional management promotes a rich biodiversity in both grasslands and arable systems in Hungary. Agri-environment schemes were introduced when Hungary joined the EU in 2004; however, their influence on biodiversity has not been systematically monitored.

Conclusions Insights emerging from farmland bird research in those European countries which still practice extensive agricultural techniques could be used to set general baseline targets for restoring biodiversity in regions where farmlands are now intensively managed. At the European scale urgent tasks are to: (1) investigate the relationships between management and bird diversity and density on a much wider geographical scale, (2) evaluate the geographical generality of the existing evidence base (which is mainly based on studies conducted in more intensively farmed regions), and (3) enhance the policy impact of conservation research.     

Hunting and the fate of French breeding waterbirds

Capsule French breeding populations of hunted waterbirds have more negative long-term population trends than closely related non-hunted species.

Aims To assess the relative fate of breeding populations of hunted and non-hunted waterbird species in France.

Methods We compared long-term population growth rates of hunted versus non-hunted waterbirds using two large-scale and long-term national surveys.

Results Waterbirds globally displayed long-term increases in population sizes most likely driven by their positive response to the implementation of numerous protected areas over remnant wetlands across the country since the early 1970s. In contrast, hunted species revealed more negative trends compared to non-hunted species.

Conclusion A causal relationship between hunting and population dynamics is not demonstrated here, but the results are consistent with species' breeding populations being negatively affected, on average, if they are hunted.