Cereal-based wholecrop silages: A potential conservation measure for farmland birds in pastoral landscapes

Declines of farmland birds have been pronounced in landscapes dominated by lowland livestock production and densities of seed-eating birds are particularly low in such areas. Modern livestock production often entails a simple cropping system dominated by ley grassland and maize grown for animal feed. These crops often lack invertebrate and seed resources for foraging birds and can be hostile nesting environments. Cereal-based wholecrop silages (CBWCS) offer potential benefits for farmland birds because they can be grown with minimal herbicide applications and can be spring-sown with following winter stubbles. We compared the biodiversity benefits and agronomic yields of winter-sown wheat and spring-sown barley as alternatives to grass and maize silage in intensive dairy livestock systems. Seed-eating birds foraged mainly in CBWCS fields during summer, and mainly on barley stubbles during winter and this reflected the higher densities of seed-bearing plants therein. Maize and grass fields lacked seed-bearing vegetation and were strongly avoided by most seed-eating birds. Production costs of CBWCS are similar to those of maize and lower than those of grass silage. Selective (rather than broad-spectrum) herbicide application on spring barley crops increased forb cover, reduced yields (by 11%) but caused only a small (<4%) increase in production costs. CBWCS grown with selective herbicide and with following winter stubbles offer a practical conservation measure for seed-eating farmland birds in landscapes dominated by intensively-managed grassland and maize. However, the relatively early harvesting of CBWCS could destroy a significant proportion of breeding attempts of late-nesting species like corn bunting (Emberiza calandra) or yellow wagtail (Motocilla flava). Where late-breeding species are likely to nest in CBWCS fields, harvesting should be delayed until most nesting attempts have been completed (e.g. until after 1st August in southern Britain).     

Autumn-sowing of cereals reduces breeding bird numbers in a heterogeneous agricultural landscape

The switch from spring-sown to autumn-sown cereals and the loss of habitat heterogeneity are often suggested to be key drivers of breeding bird decline on arable farmland. Yet, both factors are interlinked and it remains uncertain whether autumn-sown cereals reduce breeding bird numbers also in the structurally complex arable farmland of northern Europe. We tested whether autumn-sowing of cereals at both local and landscape scales affected the breeding bird community in a heterogeneous agricultural landscape of south-central Sweden. Rotation between sowing types was used as a semi-experiment based on 34 spring- vs. 41 autumn-sown cereal plots centred on infield non-crop islands of similar structure, size and surroundings. Species richness and territory abundance of ground-foraging species were significantly lower in autumn- than in spring-sown cereal plots both in the crop fields and the infield non-crop islands during the breeding season. No such effect was observed among foliage gleaning birds. Species richness in spring-sown cereal plots was less the more autumn-sown crops in the surrounding landscape within a 500 m radius. Average skylark densities did not differ between autumn- and spring-sown cereal plots because habitat preferences changed; densities declined in autumn-sown cereals during the growing season whereas they increased on spring-sown fields which had shorter swards throughout the breeding season. Our results indicate that negative effects of autumn-sown crops on breeding bird numbers spill over into both neighbouring non-crop and crop habitats. We conclude that agri-environmental schemes should place more emphasis on facilitating the value of the cropped area of fields as a foraging and nesting habitat. The retention of various non-crop habitats alone may not provide sufficient food close to nest sites for farmland birds that rely on crop fields for foraging.     

Acacia, cattle and migratory birds in southeastern Mexico

Acacia pennatula groves in mid-elevation valleys of southern Mexico supported both the highest density and diversity of migratory birds compared to other habitats in the region. In addition, we found the highest numbers for over half of the common migratory species. Despite the high degree of leaf loss during the late winter, acacia groves do not experience greater declines in insectivorous migratory bird populations than other local habitats. Color-marked individuals of canopy species had a strong tendency to remain resident within a single acacia grove throughout the winter. Management of native acacias on subtropical rangelands for wood products, fodder, and soil improvement would probably directly and indirectly benefit migratory song bird populations. Neotropical acacia woodland is primarily associated with grazing land for livestock which might discourage some from considering acacia management a viable option for migratory bird conservation. However, acacias were probably widespread in recent geologic time under drier conditions with heavy browsing and seed dispersal by a now extinct megafauna. Two observations suggest a foraging advantage for acacia use: the higher density of migratory birds in acacia is a result of higher numbers of canopy insectivores; and acacias are selected by migrants when they occur in mixed habitat. We hypothesize that plant investment in mechanical defenses (thorns) reduces energy available for chemical defenses effective against insect herbivores.     

Conserving bird species in Japanese farmland: Past achievements and future challenges

A high proportion of threatened and near-threatened species in the world now inhabit farmland. Although much data regarding the impact of agriculture on farmland biodiversity have been accumulated in Western countries, such information, particularly on the impact of rice cultivation, is fragmentary in other parts of the world and has rarely been disseminated internationally. Therefore, this paper aims to clarify what information has become available through earlier studies in Japan, where farmland mainly consists of rice paddy areas, and give directions for future studies about the impact of agriculture on farmland birds in Japan. This study made three notable observations. First, a review of earlier studies of farmland bird species in Japan uncovered some evidence of both increases (e.g., wildfowl and cranes) and declines (e.g., waders) in population size. Second, this paper closely examined case studies of two types of typical farmland birds: (1) geese and cranes foraging on crops and/or harvested remains of crops and (2) waders and egrets foraging on small organisms in farmland, not agricultural crops. This portion of the study identified some potential routes through which human activities in farmland affect bird species in Japan, and offered practical implications for conservation and management of these species supported by scientific data. Finally, based on the results of this review, three key tasks for future conservation studies and practices in Japanese farmland were suggested: (1) establishing quantitative indices based on monitoring surveys in farmland to track the population status, (2) collecting further evidence of the impact of agriculture, particularly on population-level responses by birds, and in a food-web context, and (3) applying evidence-based conservation to practice.     

Effects of age and intensity of urbanization on farmland bird communities

Urban sprawl is now occurring worldwide and considered as a major large-scale perturbation on ecosystems. Consequently, urban territory is replacing other habitats such as agricultural areas. As farmland biotic communities are already reported to be declining, it seems necessary to assess the urbanization impact on them. We conducted a bird survey on 92 plots of 1 × 1 km chosen after stratification on the proportion of urban area and farmland habitat (either 0%, 25%, 50%, 75%), focusing on farmland habitat. Two aspects of urbanization were studied: its intensity and its age. We found that farmland bird species richness did not vary with increasing proportion of urbanized habitat. Non-farmland bird species richness increased from 0% to 25% classes and was constant for other classes. No effect of the urbanization age on farmland bird species richness was found, whereas a positive one was found on the non-farmland birds’ species richness. Abundance of the most specialized farmland birds decreases with urbanization intensity and age. We also found that, the more urbanized and the more recently urbanized the plots, the more similar bird communities. A strong difference in farmland bird’s communities’ compositions was found between 0% and 25% of urbanization, whereas no distinction was found between 50% and 75%. Altogether, our results suggest that to maintain for farmland birds, it is better to add new urban habitat in place where it already exist, rather than to spread it in small lots throughout the landscape.     

Facilitating the evolution of resistance to avian malaria in Hawaiian birds

Research has shown that avian malaria plays an important role in limiting the distribution and population sizes of many Hawaiian birds, and that projected climate change is likely to eliminate most disease-free habitat in Hawai’i in the next century. I used a modeling approach, parameterized with demographic data from the literature and the field, to examine alternate management scenarios for the conservation of native Hawaiian birds. I examined the feasibility of using management in the form of rodent control to facilitate the evolution of resistance to malaria by increasing the survival and reproduction of native birds. Analysis of demographic data from seven native species, Akepa (Loxops coccineus), ‘Akohekohe (Palmeria dolei), Elepaio (Chasiempis sandwichensis), Hawai’i’amakihi (Hemignathus virens), Hawai’i creeper (Oreomystis mana), Omao (Myadestes obscurus), and Palila (Loxioides bailleui), suggest that differences in life history cause some species to be more susceptible to local extinctions from the transmission of malaria. Modeling results demonstrated that rodent control at middle, but not high, elevations can facilitate the evolution of resistance to malaria in several species of Hawaiian birds. Advocating a management approach that encourages evolutionary change in endangered species contrasts with the traditional conservation paradigm but it may be the best strategy to reduce the impacts of one of the multiple stressors that have devastated the native bird community of Hawai’i.     

Map of bird sensitivities to wind farms in Scotland: A tool to aid planning and conservation

Government targets for renewable energy have led to a huge increase in wind farm proposals. Because of its high wind resource, Scotland has more proposed wind farms than any other UK country. Scotland’s upland habitats support many birds of conservation concern, leading to potential conflict with wind farms.To help reduce this conflict, a map of bird sensitivities has been created to guide the location of onshore wind farms in Scotland, based on distributions of 16 bird species of conservation priority and statutory Special Protection Areas. The likely sensitivity of each species to wind farms was assessed from literature, based on foraging ranges, collision risk and sensitivity to disturbance. This information was used to buffer species’ locations to identify areas of ‘high’ or ‘medium’ sensitivity. Individual species maps were converted to 1-km square resolution, and a composite map for all species created by selecting the highest sensitivity rating for each square.The map indicates greater bird sensitivity in northwest Scotland, particularly the Highlands, Western and Northern Isles. Overall, 37% of Scotland is classified as ‘high’, 25% as ‘medium’ and 38% as ‘low/unknown’ sensitivity. The overlap of the mapped species with proposed and existing wind farm developments was assessed and species for which cumulative effects of multiple wind farms are of particular concern identified. Within a Scottish context, bean goose, red kite and hen harrier showed the greatest overlap. Applications and limitations of the approach are discussed.     

Specialist response to proportion of arable land and pesticide input in agricultural landscapes

Increases in farming practice intensity and landscape simplification are two well-known threats for many farmland bird species. Nevertheless, the effects of these two factors may differ strongly among species. Here, we propose to use the specialist-generalist concept to assess which bird species are most affected by these two factors. Bird density and intensity of farming practices were assessed within a sample of 58 farms across the Seine-et-Marne region in France, using point counts and a standardised farmer survey. The local abundance of 41 farmland and non-farmland species was related to farming intensity (pesticide applications) and landscape simplification (proportion of arable land), which was quantified using generalised least square models to account for spatial autocorrelation. The more specialised the farmland and non-farmland birds were, the more negatively affected they were by the intensity of farming practices, relative to the generalist bird species. Local habitat simplification had a more positive effect on abundance of the most specialist farmland bird species. This latter relationship was not significant when tested at a landscape scale, which strongly suggests that the sensitivity of farmland specialists to landscape simplification is scale-dependent. Some non-farmland species’ abundance was also reduced by farming intensity and local landscape simplification suggesting that low-input agri-environmental measures could benefit both farmland and non-farmland specialists, regardless of local and landscape habitat context. However, if diversity-enhancing measures should benefit non-farmland populations, it is likely that they do not favour farmland specialist species which are more at risk. We suggest designing of priority areas for farmland specialist birds, and landscape managing accordingly.     

Maximizing re-introduction success: Assessing the immediate cost of release in a threatened waterfowl

Translocations have become one of the most commonly used tools for biodiversity restoration worldwide, however one out of three re-introduction plans fails to create a viable population or to successfully reinforce the existing one. We used results from the analysis of individual-based information on the re-introduction of a threatened waterfowl species, the crested coots Fulica cristata, to provide guidelines to maximise re-introduction success. We found that about a third of the post-release mortality took place within the first month after release. This immediate ‘cost of release’ in terms of local survival or ‘release risk factor’ seems to be a common feature of re-introduction projects, and it is likely due to the inexperience of captive-born individuals to face the new environment. This hypothesis was supported by the positive association between survival and time spent in the wild Results suggested that coots released between February and May have a slightly higher survival. A joint measure of survival and breeding probabilities indicated that birds released in late winter (February-March) had a higher chance to survive and reproduce compared to birds released later in the year. From an applied perspective our results can be used within an adaptive management framework to determine the optimum period of release, providing substantial support for future decision-making in the management of waterfowl, and other long-term projects of re-introduction of threatened vertebrate species.     

Tolerance of frugivorous birds to habitat disturbance in a tropical cloud forest

In view of the continued decline in tropical forest cover around the globe, forest restoration has become a key tool in tropical rainforest conservation. One of the main - and least expensive - restoration strategies is natural forest regeneration. By aiding forest seed influx both into disturbed and undisturbed habitats, frugivorous birds facilitate forest regeneration. This study focuses on the tolerance of a frugivorous bird community to anthropogenic habitat disturbance within the broader context of natural forest regeneration with conservation purposes. It was carried out in the tropical cloud forest of Costa Rica’s Talamanca Mountains. Bird community response and tolerance to habitat disturbance was assessed by comparing bird presence and densities along a disturbance gradient, ranging from open pastures to closed mature forests. Birds were censused along nine transects applying the variable width line transect procedure. Forty relevant frugivorous bird species were observed during 102 h of survey time. Densities were calculated for 33 species; nine species responded negatively to increasing level of disturbance and nine others positively. Results indicate that large frugivores are generally moderately tolerant to intermediate, but intolerant to severe habitat disturbance, and that tolerance is often higher for medium and small frugivores. It appears that moderately disturbed habitats in tropical cloud forests are highly suitable for restoration through natural regeneration aided by frugivorous birds. Due to a lack of large forest seed dispersers, severely disturbed habitats appear less suitable.     

Landscape-moderated importance of hedges in conserving farmland bird diversity of organic vs. conventional croplands and grasslands

Hedges provide important nesting, feeding and sheltering sites for birds in agricultural areas, while organic farming also enhances farmland birds. However, it is little known how the interaction of these local variables (amount of hedges and organic management) with landscape scale variables affects birds. We selected paired conventional and organic winter wheat fields and meadows in each of 10 landscapes in Germany. Birds were surveyed in the fields and in the adjoining hedges. More bird species occurred in organic than in conventional fields regardless of land-use type (wheat fields and meadows). However, hedge length had a much stronger effect on bird richness than organic farmland management. We found an interaction of landscape complexity and hedge length in that hedge length enhanced bird richness only in case of simple landscapes (<17% semi-natural areas within a 500 m radius around the centre of bird survey plots). In more complex landscapes the local effect of hedge length levelled off because bird richness was high even without local hedges. Therefore, adding hedges or introducing organic farming practices should be primarily promoted in simple landscapes, where it really makes a difference for biodiversity.     

Crofting and bumblebee conservation: The impact of land management practices on bumblebee populations in northwest Scotland

The northwest of Scotland is a stronghold for two of the UK’s rarest bumblebee species, Bombus distinguendus and Bombus muscorum. The predominant form of agricultural land management in this region is crofting, a system specific to Scotland in which small agricultural units (crofts) operate rotational cropping and grazing regimes. Crofting is considered to be beneficial to a wide range of flora and fauna. However, currently there is a lack of quantitative evidence to support this view with regard to bumblebee populations. In this study we assessed the effect of land management on the abundance of foraging bumblebees and the availability of bumblebee forage plants across crofts in northwest Scotland. The results of our study show that current crofting practices do not support high densities of foraging bumblebees. Traditional crofting practice was to move livestock to uplands in the summer, but this has been largely abandoned. Summer sheep grazing of lowland pasture had a strong negative impact on bumblebee abundance and forage plant availability throughout the survey period. The use of specific ‘bird and bee’ conservation seed mixes appears to improve forage availability within the crofted landscape, although the number of bees observed remained low. Of the forage plants available, the three most frequently visited species were from the Fabaceae. We therefore conclude that the creation of agri-environment schemes which promote the use of Fabaceae-rich seed mixes and encourage the removal of sheep grazing on lowland areas throughout the summer are essential in order to conserve bumblebee populations within crofted areas.     

Distance to edges, edge contrast and landscape fragmentation: Interactions affecting farmland birds around forest plantations

Afforestation often causes direct habitat losses for farmland birds of conservation concern, but it is uncertain whether negative effects also extend significantly into adjacent open land. Information is thus required on how these species react to wooded edges, and how their responses are affected by edge and landscape characteristics. These issues were examined in Mediterranean arable farmland, using bird counts at 0, 100, 200, 300 and >300 m from oak, pine and eucalyptus edges, embedded in landscapes with variable amounts and spatial configurations of forest plantations. Bird diversity declined away from edges, including that of woodland, farmland and ground-nesting birds. Positive edge responses were also found for overall and woodland bird abundances, and for five of the nine most widespread and abundant species (Galerida larks, stonechat, linnet, goldfinch and corn bunting). Strong negative edge effects were only recorded for steppe birds, with reduced abundances near edges of calandra larks and short-toed larks, but not of little bustards and tawny pipits. Edge contrast affected the magnitude of edge effects, with a tendency for stronger responses to old and tall eucalyptus plantations (hard edges) than to young and short oak plantations (soft edges). There were also species-specific interactions between edge and fragmentation effects, with positive edge responses tending to be strongest in less fragmented landscapes, whereas steppe birds tended to increase faster away from edges and to reach the highest species richness and abundances in large arable patches. Results suggest that forest plantations may increase overall bird diversity and abundance in adjacent farmland, at the expenses of steppe birds of conservation concern. Clustering forest plantations in a few large patches and thus reducing the density of wooded edges at the landscape-scale might reduce such negative impacts.     

High sensitivity of montane bird communities to habitat disturbance in Peninsular Malaysia

Over the past few decades, the montane forests of Peninsula Malaysia have been severely impacted by the cultivation of exotic crops and urban sprawl. To guide conservation initiatives, montane bird communities were studied to determine their response along a disturbance gradient with the aim of identifying key factors influencing their distribution. Habitat types surveyed included primary and secondary montane forests, a tea plantation, rural, and urban areas in Cameron Highlands and Fraser’s Hill. Response variables included species richness and density quantified via point counts and mistnet surveys. Explanatory variables measured were related to vegetation structure, food abundance and land-use cover. Estimated ‘true’ species richness was higher for pristine and minimally disturbed sites, lower in tea plantation and lowest in heavily developed town centres. Nonmetric multidimensional scaling revealed that both vegetation structure (e.g. canopy density) and land-use cover (e.g. proportion of forest cover) influence species distribution; certain invasive lowland birds were tolerant of extreme development and native montane birds, in general, endured only slight habitat disturbances. A simulation indicated that montane forest dependant species richness started to decline when more than 20% of the canopy cover was lost. Less than a third of the species richness remained when more than 40% of the canopy cover was cleared. The logistic regression model suggested that sensitive species nested lower, were restricted to montane habitats and foraged in mid or high canopy. The dominance of lowland invasives in highly developed urban sites reveals that homogenisation of bird communities can occur even at higher altitudes (>1400 m a.s.l.). The results indicated that native montane birds communities are sensitive to habitat loss and degradation. Thus, any development in the highlands must proceed with minimal disturbance to montane forests, of which, keeping the canopy cover intact should be a crucial consideration.     

Threshold effect of eucalypt density on an aggressive avian competitor

General guidelines available to revegetation planners focus on the spatial context and dimensions of the revegetated site. However, site-specific habitat factors can have overarching importance for habitat value, especially where interactions with competitors or predators may play an important role. Current revegetation projects in Australia which aim to restore slow-growing buloke (Allocasuarina luehmannii) woodland, a threatened habitat important for bird conservation, usually include faster-growing eucalypts in plantings. This research aimed to identify whether eucalypt presence in buloke woodland facilitates invasion by the noisy miner (Manorina melanocephala), an aggressive competitor that is absent from pure buloke woodland. Birds were surveyed in buloke woodland remnants that contained eucalypts as a sub-dominant species at densities of 0-16 per ha. The probability of noisy miner presence in buloke woodland increased markedly where eucalypts were present at a density of approximately five per hectare. The presence of noisy miners resulted in a substantial difference in bird assemblage structure and composition. Small-bodied insectivorous birds which are experiencing population declines in southern Australia were recorded on average six times more often in transects without noisy miners (low-eucalypt density transects). Avian behaviour and habitat use was also altered, with birds flying more frequently in transects where noisy miners were present. A minor difference in habitat composition results in substantial degradation of the conservation value of non-eucalypt woodland in eastern Australia due to invasion by aggressive avian competitors. Revegetation and restoration practices should take into account the potential for such subtle floristic differences to result in substantial variation in conservation outcomes.     

Birds of different biogeographic origins respond in contrasting ways to urbanization

Impacts of urbanization on ecological systems are expected to increase during the 21st century, and identifying which species may not survive under urban constraints is of practical importance to conservation biology. I study whether a species’ biogeographic origin might be a useful predictor of vulnerability to urban pressures, and if this depends on the geographic scale of the study. By means of multivariate ordination analyses and computer intensive, Monte Carlo simulation techniques, I study the patterns of zoogeographical affinity (a proxy for biogeographic origin) of passerine birds living in 14 non-urban (NU) and 11 urban (U) sites throughout Mexico, a biodiversity rich and urbanizing country between the Nearctic and Neotropical Regions; at a regional scale, I also study differences between NU and U sites in the state of Puebla, in the ‘Temperate Sierras’ ecoregion. Differences in zoogeographical affinities between NU and U sites were statistically significant, and were mainly caused by changes in the number of neotropical and nearctic species. In terms of the ‘equivalent number of zoogeographical classes’, a useful measure of zoogeographical diversity, bird assemblages in urban settings were less diverse than those simulated by random drawings from the corresponding species pools. In fact, urbanization seems to be provoking the selective removal of neotropical and endemic species from urban assemblages, whereas at the same time retaining more-than-expected nearctic (temperate) species; birds with nearctic affinities could be successful candidates to ‘urban exploiters’ in the study case. At a landscape scale, results suggest that urbanization is creating holes in the geographic range of both neotropical passerines and birds endemic to Mexico, which are selectively removed by the urban filter, and can be identified as those more heavily threatened by urbanization if proactive strategies to conserve biodiversity in urban ecosystems are not implemented. Among other reasons for the observed patterns, the tropical niche conservatism is invoked as an explanation.     

Effects of structural and functional connectivity and patch size on the abundance of seven Atlantic Forest bird species

We studied the importance of fragment size and structural and functional connectivity on the occurrence and abundance of seven Atlantic Forest bird species in 13 patches (13-275 ha) and three sites within a continuous forest (10,000 ha). We sampled birds with point counts and evaluated structural connectivity considering the presence of corridors and the degree of isolation. We defined functional connectivity by analyzing species movements using playbacks in forest corridors between fragments and in the surrounding matrix. Species differed in their responses to fragmentation. For the frugivorous species, Trogon surrucura, Carpornis cucullatus and Triclaria malachitacea, patch size was the main factor determining abundance. Two understory insectivorous species, Basileuterus leucoblepharus and Pyriglena leucoptera, were more affected by the degree of patch connectivity, the former by the presence of corridors and the latter by the distance between patches. The capacity of P. leucoptera to use corridors and open areas (i.e. functional connectivity) shaped its abundance pattern. Fragmentation had no effect on the abundance of Chiroxiphia caudata and had a positive effect on Batara cinerea. This study emphasizes the importance of considering species’ perceptions of landscape, especially functional connectivity, in understanding the effects of habitat fragmentation.     

Estimating the potential effects of sudden oak death on oak-dependent birds

Sudden oak death (SOD), a disease induced by the fungus-like pathogen Phytophthora ramorum, threatens to seriously reduce or eliminate several oak species endemic to the west coast of North America. We investigated how the disappearance of one of these species, coast live oak (Quercus agrifolia), may affect populations of five resident oak-affiliated California birds - acorn woodpecker (Melanerpes formicivorus), Nuttall’s woodpecker (Picoides nuttallii), Hutton’s vireo (Vireo huttoni), western scrub-jay (Aphelocoma californica), and oak titmouse (Baeolophus inornatus) - using geocoded data from Audubon Christmas Bird Counts, North American Breeding Bird Surveys, and the California Gap Analysis. Capitalizing on observed relationships between the focal bird species and both oak species diversity and areal extent, we modeled relative bird abundance while assuming complete loss of Q. agrifolia and complete, partial, or no loss of oak habitat following a disease sweep. Post-SOD projections of bird populations occurring within the range of coast live oak were on average 25-68% smaller and 13-49% more variable relative to pre-SOD estimates. SOD effects were greatest for habitats with low initial oak species diversity. Climatic SOD models predicted that the disease stands to negatively impact populations of all five focal bird species throughout 20% of California’s coast live oak habitats. This study provides the first spatially explicit insights into the potential effects of SOD on avian distribution and abundance. Results may be used to help prioritize conservation plans aimed at minimizing overall community level disturbances resulting from the disease.     

Could soil degradation contribute to farmland bird declines? Links between soil penetrability and the abundance of yellow wagtails Motacilla flava in arable fields

Major changes to the extent and quality of farmland habitats, brought by the intensification of agricultural practice, are thought to be the main factors driving declines in a suite of farmland bird species in Europe. Recent changes in agricultural techniques have also contributed to widespread soil degradation, arising from increased soil exposure to erosion forces, declining soil organic content and increasing soil compaction. Although soils have a fundamental influence on ecosystem properties, the implications of soil degradation for farmland biodiversity have received little attention. In this study, we measure the influence of soil conditions on the distribution of a declining insectivorous farmland bird, the yellow wagtail Motacilla flava, relative to other habitat features in arable fields. Soil penetrability was found to have a significant influence on the abundance of territorial yellow wagtails at the field scale, together with crop type. Other measured habitat features had little effect on territory abundance, including soil organic content, crop height (within preferred crop types), field boundary habitats and availability of bare ground. Monitoring of invertebrate abundance across 20 cereal fields revealed a significant influence of both soil penetrability and soil organic content on aerial invertebrate capture rates. This relationship was strongest during the latter part of the breeding season, implying that settling yellow wagtails could use soil penetrability as a predictive indicator of prey abundance during the chick-rearing period. The strong relationship between yellow wagtails and soil penetrability suggests a potential causative link between soil degradation and population decline. The role of soils in determining abundance patterns and population declines of other farmland species may have been overlooked in previous studies.