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The influence of livestock management on habitat quality for farmland birds
Abstract
Abstract This review covers research linking foraging habitat quality for birds to livestock management in lowland farmland. Based on this research we propose a framework for predicting the value of grazing systems to birds. This predictive framework is needed to guide the development of agri-environment measures to address farmland bird declines in pastoral areas. We show that the exacting requirements of declining granivorous birds pose the greatest challenges, while the needs of soil invertebrate feeding species are more easily met.
... Grasslands grazed at low intensity (<0.5 animal units per hectare, where 1 animal unit = 500 kg [Andresen et al. 1990]) seems to benefit many grassland-associated bird species, enhancing foraging and nesting opportunities (Buckingham & Peach 2005;Pärt & Söderström 1999). For instance, the abundances of the Eurasian Skylark Alauda arvensis, Red-backed Shrike Lanius collurio or Meadow Pipit Anthus pratensis were found to be higher with low-intensity grazing in the breeding season, and birds seem to profit from increased food availability resulting from the grazers' activity (Ceresa et al. 2012;Evans et al. 2006;Kohler et al. 2016). ...
... For instance, the abundances of the Eurasian Skylark Alauda arvensis, Red-backed Shrike Lanius collurio or Meadow Pipit Anthus pratensis were found to be higher with low-intensity grazing in the breeding season, and birds seem to profit from increased food availability resulting from the grazers' activity (Ceresa et al. 2012;Evans et al. 2006;Kohler et al. 2016). Conversely, intense grazing (>2.0 animal units per hectare) may only favor birds like Thrushes, Turdus sp, that exploit very short vegetation when feeding on soil invertebrates (review by Buckingham & Peach 2005). ...
... In winter, however, grazed areas seemed to be important for woodland-foraging birds as well. These patterns are likely due to the open habitat maintained by grazers (Leal et al. 2019) that provides better food availability, prey visibility, and predator detectability for birds (Buckingham & Peach 2005;Cox et al. 2014;Whittingham & Evans 2004). ...
Context
Grazing by large herbivores is an increasingly used management tool in European nature reserves. A challenge in grassland conservation is to maintain both the openness and the heterogeneity of the habitat, to support their animal communities, including birds. Horses and cattle are often used to create and maintain patchy landscapes, especially in rewilding projects, but the influence of grazers on birds is often debated by conservationists.
Objectives
We studied how the abundance and species richness of birds of four foraging guilds are related to the area use of Highland cattle and Konik horses in an alluvial grassland. We also investigated how season and land cover influences the spatial distribution of individuals and species of different bird guilds on the grazed area.
Methods
We equipped all grazers with GPS-collars to assess the density of their hourly positions. We made weekly transect counts of birds to describe their distribution and carried out land cover surveys to describe the habitat. We used GAMM models in a spatially explicit framework.
Results
Open-area foraging birds were clearly associated with higher grazer densities, and aerial, wetland and woodland birds also seemed to profit from low-intensity year-round grazing. Most bird species and individuals were observed on open landscapes scattered with woody patches and waterbodies, and on areas with moderate grazer density. The number of birds on the grazed area was about twice the number on the ungrazed control area.
Conclusions
A heterogenous landscape maintained by low-intensity grazing seems to fulfil the needs of birds with different feeding ecologies.
... Grasslands grazed at low intensity (< 0.5 animal unit per hectare) seems to provide particularly good foraging conditions and nesting sites for almost all grassland-associated bird species (Buckingham & Peach 2005;Pärt & Söderström 1999). For instance, the abundance of the Eurasian Skylark Alauda arvensis, Red-backed Shrike Lanius collurio or Meadow Pipit Anthus pratensis were higher with lowintensity grazing in the breeding season, as these birds are likely able to pro t from the food availability in heterogenous habitats that result from the grazers' activity (Ceresa et al. 2012;Evans et al. 2006; Kohler et al. 2016). ...
... In contrast, intense grazing (> 2.0 animal unit per hectare) may only increase densities of birds that can exploit homogenous, very short vegetation or bare ground, such as Thrushes, Turdus sp, which feed on soil-dwelling invertebrates (review by Buckingham & Peach 2005). Species richness among open-area associated birds was higher in low-and moderately grazed areas, and lower in areas with high densities of grazers (Batary et al. 2007). ...
... In winter, however, grazed areas seemed to be important for woodlandforaging birds as well. These patterns are likely due to the open habitat maintained by grazers (Leal et al. 2019) that provides better food availability, prey visibility, and predator detectability for birds (Buckingham & Peach 2005;Cox et al. 2014;Whittingham & Evans 2004). Our results are in line with earlier suggestions that due to the different ecology of the different foraging guilds, the actual presence of birds on a grazed area depends also on the season and habitat cover, not only on grazer densities (Laiolo 2005). ...
Context
Grazing by large herbivores is an increasingly used management tool in European nature reserves. A challenge in grassland conservation is to maintain both the openness and the heterogeneity of the habitat, to support their animal communities, including birds. Horses and cattle are often used to create and maintain patchy landscapes, especially in rewilding projects, but the influence of grazers on birds is often debated by conservationists.
Objectives
We studied how the abundance and species richness of birds of four foraging guilds are related to the area use of Highland cattle and Konik horses in an alluvial grassland. We also investigated how season and landcover influences the spatial distribution of individuals and species of different bird guilds on the grazed area.
Methods
We equipped all grazers with GPS-collars to assess the density of their hourly positions. We made weekly transect counts of birds to describe their distribution, and carried out landcover surveys to describe the habitat. We used GAMM models in a spatially explicit framework.
Results
Open-area foraging birds were clearly associated with higher grazer densities, and aerial, wetland and woodland birds also seemed to profit from low-intensity year-round grazing. Most bird species and individuals were observed on open landscapes scattered with woody patches and waterbodies, and at areas with moderate grazer density. The number of birds on the grazed area was about twice as on the ungrazed control area.
Conclusions
A heterogenous landscape maintained by low-intensity grazing seems to fulfil the needs of birds with different feeding ecologies.
... Gibson et al., 1992;Vickery et al., 2001;Batáry et al., 2007;Dennis et al., 2008). However, access to prey can be just as important for birds as prey abundance (Buckingham and Peach, 2005), and grazing may also influence this parameter through its effect on vegetation height and density (Fuller and Gough, 1999). This is very important for ground-foraging birds because they may struggle to find and capture food in dense ground cover or even avoid it altogether to minimize predation risk (Buckingham and Peach, 2005). ...
... However, access to prey can be just as important for birds as prey abundance (Buckingham and Peach, 2005), and grazing may also influence this parameter through its effect on vegetation height and density (Fuller and Gough, 1999). This is very important for ground-foraging birds because they may struggle to find and capture food in dense ground cover or even avoid it altogether to minimize predation risk (Buckingham and Peach, 2005). ...
... However, information to guide management is very scarce and is mostly based on studies done in temperate grasslands of central and northern Europe (e.g. Buckingham and Peach, 2005;Buckingham et al., 2006;Evans et al., 2006;Hartel et al., 2014) where conditions are potentially very different from those prevailing in their southern wooded counterparts. Moreover, even in those better studied regions virtually all existing information has been obtained during the nesting season and there is little information for the winter (e.g. ...
Wooded grasslands, usually grazed, cover vast areas in Southern Europe and Northern Africa. They host rich resident bird communities and, in winter, receive large numbers of migrants from Central and Northern European woodlands. Many species are partly or entirely dependent on ground foraging and, since in winter food is often the most limiting factor for birds, maintaining suitable ground habitat is crucial.
To study how grazing influences suitability of winter ground habitat for birds, we carried out an experiment in a wooded grassland in Southern Iberia, whereby grazing was controlled in 12 purposely fenced two-hectare plots (4 × 15 sheep/ha, 4 × 3 sheep/ha and 4 × no grazing). We quantified ground habitat features, food abundance and intensity of use by ground-foraging birds in each of these 12 plots. In addition, we made focal observations of birds feeding on the ground and compared the habitat of 1m2 foraging patches with those of nearby control patches.
We found that virtually all birds prefer to forage in patches with short ground vegetation and high food abundance. Measurements of these parameters in the experimental plots showed that while grazing shortens vegetation it decreases food availability, and thus has opposing effects on important determinants of habitat suitability. Nevertheless, the numbers of birds foraging in the plots indicate that, overall, grazing benefits the assemblage of ground-feeding birds, presumably because for most species the advantages of foraging in less cluttered habitats more than compensate the lower abundance of prey. However, arboreal bird species that make short foraging forays to the ground had lower numbers in grazed plots.
Most bird species that forage on the ground benefited from grazing, and although they can forage under a broad range of grazing levels, some showed clear preferences along the gradient of grazing intensity. Such preferences should be taken into consideration by managers. In general, grazing should be maintained at a level sufficient to open up ground vegetation, increasing the area occupied by patches of short vegetation, in which almost all bird species prefer to forage. At moderate levels, grazing is thus a valuable management tool to promote winter bird habitat quality in Mediterranean wooded grasslands, while increasing the economic value of these threatened landscapes.
https://authors.elsevier.com/a/1XyWZcA-IW0PX
... Environmental gradients across the European lowlands have become simplified along with a general reduction of biodiversity in farmland (Robinson & Sutherland 2002), reducing heterogeneity and functioning across trophic levels (Donald et al. 2001, Chamberlain & Fuller 2000. As a first step towards limiting damage to ecosystems and species, it is crucial to identify those components of the farming landscape that are used by key species, why they are used, and whether it might be feasible to alter characteristics of those unused areas for the benefit of the species (Buckingham & Peach 2005, Atkinson et al. 2005, Vickery et al. 2001. In this paper, we examine factors influencing spatial use of components of a UK agricultural landscape by Green Woodpeckers Picus viridis. ...
... Vegetation height and structure clearly affected feeding-site choice, and other studies on ground feeding birds e.g. Sky Lark Alauda arvensis (Chamberlain et al. 1999) in farmland have found that accessibility affects occupancy (see Buckingham & Peach (2005) for a review). Green Woodpeckers are known to be sensitive to changes in grazing intensity affecting ant distribution and abundance related to height of the grass sward (Cramp et al. 1998) and presumably also to the accessibility of prey. ...
... Our findings concur with Muschketat & Raqué (1993), who found that not all ant species within the home-ranges of Green Woodpeckers were taken by the birds and this was related to habitat structure affecting accessibility. One example from our study is the lack of Green Woodpecker feeding locations in rank grassland or woody vegetation associated with edge habitats, probably reflecting the difficulty of finding a patchily distributed prey resource with an increased risk of predation (McCollin 1998, Buckingham & Peach 2005. ...
Capsule Green Woodpeckers exhibited strong feeding‐site preference, choosing areas based on abundance of ants with additional micro‐habitat effects.
Aims To identify the habitat characteristics influencing feeding‐site selection across farmland.
Methods A pair of Green Woodpeckers was radiotracked during a breeding season. Habitat and prey abundance variables were compared within the birds’ combined home‐ranges. canoco was used to identify ecological gradients, and logistic regression used to predict feeding‐site use based on ant abundance with resultant residuals correlated to identify habitat features that further influenced site selection.
Results Most feeding was done in sheep‐grazed pastures and garden lawns with arable and cattle‐grazed land avoided. Green Woodpecker feeding sites were associated with areas of short grassland with high plant richness and high densities of ants, especially Lasius flavus. Logistic regression correctly classified 98% of cases from ant abundance. The woodpecker pair had a greater probability of feeding in areas with deep leaf litter, high plant species richness, and lower probability if the site had tall or dense vegetation, or heavily compacted soils.
Conclusions Structural habitat characteristics were important, with this woodpecker pair foraging in short grazed and mown grasslands. If these results are replicated elsewhere then appropriate farm management may benefit Green Woodpeckers significantly.
... Due to agriculture intensification, farmland birds are one of the most declining bird groups across Europe (Inger et al., 2015). One example of this intensification is change in dairy milk farms; currently cows are more often kept indoors than on traditional pastures (Buckingham and Peach, 2005;Gaworski, 2016). This trend is also evident in regions with less intensive agriculture, such as central Europe (Chabuz et al., 2012;Gaworski, 2016). ...
... The high numbers of livestock raised outdoors in this region, compared to many other parts of the country which have changed mainly to an indoor dairy system (Gaworski, 2016;Chodkiewicz and Stypiński, 2017), may partially explain the very high density of white storks in this region, in comparison to Polish, as well as, to other populations in the eastern part of the species range (Tryjanowski et al., 2005;Vaitkuviene and Dagys, 2015;Gotkiewicz and Wittbrodt, 2019). A positive association with the presence of cattle has already been described for many bird species, from small passerines to wading birds and egrets (Dinsmore, 1973;Buckingham and Peach, 2005;Chabuz et al., 2012;Chodkiewicz and Stypiński, 2017;Tóth et al., 2018), and has been linked mainly to better access to food and greater food availability, mainly invertebrates. White storks catch insects (Kosicki et al., 2006;Kwieciński et al., 2017) which were their dominant food in the study area. ...
Recent changes in agriculture have had a very strong impact on avian populations, but detailed mechanistic explanations are scarce. Some proposed solutions to avian declines can be complicated because responses are not linear. For example, abandoning pasture management can be detrimental to many open-nesting birds, but also to some others, because livestock perform ecosystem engineering, changing sward height and creating microhabitats for invertebrates, as well as for insectivorous mammals. Both these features affect the foraging efficiency of birds, for example white stork Ciconia ciconia. We studied the foraging activities of storks in the presence and absence of grazing cows, and we show that in extensive farmland in NE Poland, the presence of cows has a highly significant effect on stork foraging efficiency (in our study area mainly catching insects), which may be crucial to improving breeding success. Our results may also be important from a practical point of view. In white stork recovery projects where supplementary food is offered to storks (e.g. chicken and fish provided on feeding platforms) we believe that establishing extensive cattle pastoralism would be better from an ecological as well as from an aesthetical viewpoint.
... Agricultural environments impact populations of wild plant and animals, with farm animals in agricultural areas interacting with the environment in several different ways (Buckingham & Peach 2005). In general, the presence of livestock may be considered to function at two levels in an ecosystem. ...
... At one level there are concerns about chemical impacts such as the input of nutrients and other substances, including toxins to the soil and atmosphere. At a second level, livestock are a component of the environment and interact with other species (Söderstrom et al. 2001;Buckingham & Peach 2005). Some of these associations between domestic and wild animals, such as birds, can be commensal and mutualistic (sensu Holland & Bronstein 2008, Källander 1993. ...
Capsule The presence of farm animals increases the amount of larger insect prey (mainly large Diptera and Coleoptera) and decreases the proportion of smaller prey (Hymenoptera).
Aims To determine the relationships between presence of farm animals and diversity of diet of nestling Barn Swallows from 52 colonies located at sites with and without livestock.
Methods Diet was determined on the basis of faecal analysis. We used two approaches to quantify livestock based on their spatial distribution – a breeding site-focused approach and a village-focused approach.
Results Our results show a relationship between the presence of livestock and the size, number and composition of insect prey detected in the diet of nestling Barn Swallows. The results from the two approaches we used in our study were broadly consistent, although effects varied according to the number and types of animal being raised. The presence of domestic animals increases the amount of larger prey (mainly larger Diptera and Coleoptera) and decreases the proportion of smaller prey (Hymenoptera species). The effect of individual livestock species, mainly pigs and poultry alone, was considerably higher than the effects of pooling livestock species from Principal Component Analysis.
Conclusion Our results imply that Barn Swallows were foraging beyond the immediate area of the farm buildings in which they nest, suggest considerable adaptability in the species' diet and further emphasize the ecological role that livestock play in providing a source of prey of a required size rather specific identity. Furthermore, a statistically significant positive effect of average mass of prey (which is a direct consequence of the presence of cattle at a breeding site) on colony size suggests that livestock farming provides a more profitable prey community, which may ultimately increase local populations of Barn Swallow.
... Recent research on the diet of Dupont's lark found that this species prefers coprophagous arthropods in general (Talabante et al., 2015) and insects of the orders Coleoptera, Julida and Araneae (Zurdo et al., 2023). Other positive but not instantaneous effects of grazing on space use by steppe birds are related with increasing foraging efficiency by easing movements in open habitats (Buckingham and Peach, 2005;Leal et al., 2019;Murray et al., 2016;Zbyryt et al., 2020), while predation risk diminishes in sparser vegetation (Whittingham and Evans, 2004). Overall, a trade-off must exist between foraging efficiency, shelter, food availability and nesting requirements, as has been reported for other species (Meadow pipits Evans et al., 2015; but see effects for food availability Leal et al., 2019; for breeding success Malm et al., 2020). ...
... Dendrocopos major; Picus canus; occurrence; forest characteristics; forest birds; insects Identifying factors that determine species occurrence is a prerequisite for successful species preservation (Luck 2002, Oppel et al. 2004) and a key goal in ecological research, as it improves our understanding of fitness under various environmental and ecological conditions (Vickery et al. 2001, Atkinson et al. 2005, Buckingham & Peach 2005, Sexton et al. 2009). Models predicting the probability of species occurrence are commonly used owing to their ability to incorporate a number of variables (Carvalho & Gomes 2003). ...
... Two species typical for intensively grazed habitats, O.oenanthe and M. alba were too rare on whole B. Grahovo area (on abandonment pastures) in the second period. In addition, grassland bird species tend to be associated with either sheep or cattle, which may reflect the widely different characteristics of herbaceous vegetation in pastures stocked with each of these herbivores (Vickery et al. 2001;McCracken & Tallowin 2004;Buckingham & Peach 2005). According to Devereux et al. (2004) intensive grazing by sheep reduces sward structural complexity but moderate grazing, especially by cattle, increases structural heterogeneity and promotes short and uniform pastures. ...
We compare the avifauna between two peeriods, before and after Balkans civil conflict in a region of Western Bosnia, the municipality of Bosansko Grahovo. The present study investigated bird-abundance in 3 habitats (lokalites) of the area Pašića polje: 1) Settlements/village Luka, 2) Pastures, 3) Meadow and Agricultural land. Thirty years of data on bird numbers in breading season (from 20 th May until end of June) were analysed. By doing this we were able to capture the overall changes that happened at the landscape level and understand them in terms of ecological processes taking place at the habitat scale. Forty-six bird species were observed. We detected more species and more individuals in the period between 2004 and 2018. Our study demonstrated that abundance of the bird sgnificantly different before and after the Balkans civil conflict. Abundance of 35 species was different in the two study periods and during the first period the mean abundance was mostly lower than in the second one. Two species disappeared from the investigated localities, E. citrinella and A. campestris, while several species expanded their range or nesting site. The big decline in the Pašića polje region of some species such as the O. oenanthe, the M. alba, on the pastures, and the P. domesticus and P. pica in the settlements, can be explained by outmigration and changes in land use patterns, or non-use. Rural emigration has been complete (all population) during Balkans civil conflict and a smaller part of the population returned only after 3-5 years. Most of the changes observed support the hypothesis that the differences observed in the bird community are caused by the changes that occurred in the vegetation as a result of agricultural and grazing abandonment.
... There is obviously much research still be done in this area to support the development of suitable agri-environment measures under Pillar 2 support mechanisms. David Buckingham went on to consider the extent to which grassland management might infl uence habitat quality for farmland birds (Buckingham and Peach, 2005). His paper showed that the exacting requirements of declining granivorous birds pose the greatest challenges while the needs of soil invertebrate feeding species are more easily met under agri-environmental schemes. ...
Grazing animals cause major alterations to vegetation structure and botanical composition through their selective grazing, trampling and excretal deposition (Hester et al. , 2005). Through these effects they modify habitats and thus the populations of invertebrates and other organisms at higher trophic levels. Herbivores are thus key drivers of ecosystem function and nutrient dynamics within grazed plant communities. Changes in grazing intensity and the species mix of grazing livestock can therefore have important implications for resulting biodiversity. Ongoing reform of the European Union Common Agricultural Policy (CAP) will lead to a shift in the way financial support for livestock is distributed and hence to changes in grazing management practices. Farmers will increasingly receive financial support subject to cross-compliance with various environmental conditions and for delivery of specific environmental and social objectives. In some areas, livestock are likely to be increasingly viewed as tools for habitat management rather than solely as producers of food and other commodities.
Against this backdrop of policy change the British Society of Animal Science and the British Ecological Society organized a joint symposium at the BSAS Annual Meeting in April 2005 on the links between farm animals and biodiversity. Four papers from this symposium are presented as mini-reviews in the current issue of Animal Science.
David Oglethorpe set the policy context in his review of the environmental implications of CAP reform (Oglethorpe, 2005). His paper highlighted the likely changes in the livestock sector that will ensue including a polarization of agriculture into intensive producers versus environmental managers, increasing extensification in the uplands and some substitution of beef with sheep. Jerry Tallowin then presented a review of the impact of grazing management on grassland biodiversity (Tallowin et al. , 2005). His paper showed that lenient grazing pressure by cattle in species-rich grassland was sufficient to maintain botanical diversity but did not enhance it over a 5-year period. For species-poor grassland, grazing management could alter sward structure but, in the absence of seed sources, botanical diversity was resistant to change. There is obviously much research still be done in this area to support the development of suitable agri-environment measures under Pillar 2 support mechanisms. David Buckingham went on to consider the extent to which grassland management might influence habitat quality for farmland birds (Buckingham and Peach, 2005). His paper showed that the exacting requirements of declining granivorous birds pose the greatest challenges while the needs of soil invertebrate feeding species are more easily met under agri-environmental schemes. In the final paper by Bruno Martin, the influence of pasture diversity on cheese quality was the theme (Martin et al. , 2005). This paper reviewed recent work, primarily from France, which has examined the links between the diet of grazing animals and the sensory characteristics of various Protected Designation of Origin cheeses. The review highlighted the sometimes subtle, but none the less important influence of the grazing environment on food quality.
The purpose of the symposium was to draw together animal scientists, conservation biologists, ecologists and socio-economists to consider the changing rôle of farm livestock within the new ‘decoupled’ economic environment. Judging by the popularity of the symposium and the vibrant nature of the discussion that followed each paper, there are plenty of issues still to consider and the hope is that some of the contacts made at the meeting will yield fruitful collaborations in the future.
... A wealth of studies have examined the impact of changing grazing intensities on single taxonomic groups, typically plants or birds (see Fleischner 1994, Buckingham and Peach 2005, Diaz et al. 2007, Durant et al. 2008 for reviews). A few reviews have gone further and assessed the impact of grazing on multiple groups. ...
2015. The cascading impacts of livestock grazing in upland ecosystems: a 10-year experiment. Ecosphere 6(3):42. Abstract. Livestock grazing is a major driver of land-use change, causing significant biodiversity loss globally. Although the short-term effects of livestock grazing on individual species are well studied, a mechanistic understanding of the long-term, cascading impacts is lacking. We manipulated livestock densities using a unique, replicated upland experiment over a 10-year period and found significant effects of grazing treatment on plant and arthropod biomass; the number of Anthus pratensis breeding bird territories; the amplitude of Microtus agrestis population cycles and the activity of a top predator, Vulpes vulpes. Lower plant biomass as a result of higher stocking densities led to cascades across trophic levels, with fewer arthropods and small mammals, the latter affecting predator activity. Breeding bird territories were a function of arthropod abundance and vegetation structure heterogeneity. Our results provide a novel food-web analysis in a grazing experiment to provide a mechanistic understanding of how food-webs in upland ecosystems respond to long-term livestock grazing pressure, with consequences for management.
... At one level there are concerns about chemical impacts such as the input of nutrients and other substances, including toxins to the soil and atmosphere. At a second level, livestock are a component of the environment and interact with other species (Söderstrom et al. 2001; Buckingham & Peach 2005). Some of these associations between domestic and wild animals, such as birds, can be commensal and mutualistic (sensu Holland & Bronstein 2008, Källander 1993). ...
... Bird response to grass cutting on low-growing, small-leaved weeds such as clover Trifolium spp., and they have been shown in several studies to prefer short swards maintained by either mowing, grazing, or trampling (Kenward & Sibly 1977, Brough & Bridgman 1980, Buckingham & Peach 2005. ...
Capsule Beneficial effects of cutting grass are relatively short-lived for a range of bird species.Aims To investigate how cutting affects a range of birds occurring on farmland, how long these effects last, and whether there is any effect of the timing of cutting operations.Methods
We surveyed birds on 33 grass fields on three farms in northern England, both before and after agricultural cutting operations. The data were then modelled using generalized linear mixed models (GLMMs).Results Species relying on below-ground invertebrates (e.g. corvid species) prefer cut swards, while some species make greater use of longer grass swards (e.g. pheasant). Use of fields after cutting declined by 50 % by day 11 for corvids, by day 8 for aerial feeders (e.g. hirundines), by day 6 for gulls, and by day 4 for kestrels.Conclusions We recorded mainly common, generalist species that make use of agricultural grassland. The foraging behaviour of these species is similar to other, rarer or declining species, and so our findings can be extrapolated to a range of farmland birds. However, it is important to note that some studies indicate direct negative effects of cutting on some species not found in our surveys.
... Continuous 4 km survey transects on each site were chosen for investigation. A 300 m buffer zone was chosen to account for yellowhammer foraging ranges, this being the maximum distance they are known to forage from their territory centre during the breeding season (Stoate et al., 1998;Wilson et al., 2005;Buckingham & Peach, 2005). The study sites were digitally mapped using ArcGIS v9.3 and habitat categories within the study areas identified. ...
The results of this study give a preliminary insight into resource trade-offs that occur during breeding site selection in terms of field boundary characteristics and chick-food resources in relation to Environmental Stewardship (ES) options. Stepwise deletion of variables from a generalised linear mixed-effects model showed that the presence of a song post within a territory, presence of an ideal hedge type, hedge being cut prior to the breeding season and the absence of grass as an adjacent habitat were significantly influential in determining territory distribution. These results do not negate the value of ES summer foraging habitat, instead they highlight the importance of their location at the farm and landscape level.
... Grassland bird species tended to be associated with either sheep or cattle, which may reflect the widely different characteristics of herbaceous vegetation in pastures stocked with each of these herbivores (Vickery et al., 2001;McCracken and Tallowin, 2004;Buckingham and Peach, 2005). Intensive grazing by sheep reduces sward structural complexity and promotes short and uniform pastures, whereas moderate grazing, especially by cattle, increases structural heterogeneity and leads to patchy swards with areas of long and short cover (Devereaux et al., 2004). ...
Iberian natural steppes have traditionally been used for extensive sheep grazing, which has been noted to be positively associated with steppe bird abundance and diversity. Sheep numbers in Spain, which harbors the largest European populations of many steppe bird species, decreased by 9.2 million (37.3%) between 1992 and 2020. Steppe birds in Spain have faced dramatic declines during the same period, but there is a lack of knowledge about the potential association between sheep and open-habitat bird declines. We used sheep data from the Spanish Ministry of Agriculture and bird data (1998-2018) from the Spanish Common Bird Monitoring Program to assess the association at the Spanish scale between sheep decline and the Farmland Bird Index (FBI) and the Natural Shrub-steppe Bird Index (SBI). We also used an independent dataset on population trends of the Dupont's Lark (Chersophilus duponti) to assess the relationship between sheep numbers and the decline of this threatened steppe specialist passerine in Spain, whose European population is restricted to Iberian natural steppes. To test for a spurious relationship between temporal series, variables were tested for cointegration. After confirming cointegration, we found a strong positive relationship between sheep abundance and the trends of the FBI and SBI indices during the period 1998-2018. The association between sheep abundance and trends of the Dupont's Lark (2004-2015) was positive although it was not statistically significant. Although the main causes of decline of farmland and steppe birds are mainly related to agricultural intensification and land use changes, the correlation found, using two independent cointegrated datasets, between the reduction in farmland and shrub-steppe birds and sheep numbers at the country scale suggests that the decline of steppe birds in Spain may be also associated with the decline in sheep numbers. This agrees with previous studies that found a positive relationship between intermediate levels of sheep grazing and steppe bird abundance in Iberian steppes. Further research (e.g. experimental studies) is needed to corroborate our study and identify the most appropriate level of grazing intensity for protecting the most farmland and shrub-steppe birds. Our results suggest that the promotion of extensive grazing should be considered as a key factor in future Common Agricultural Policy reforms and conservation programmes to protect steppe birds.
Crepis senecioides is one of the endemic plant species found in Libya. The ethanol extract (E) of the flowers was partitioned on silica gel column with dichloromethane affording four compounds. Their structures were elucidated by the physicochemical and spectral data as germanicol acetate (1), 3`,3``butyl, 8`,8``carboxy) di-octyl phethalate (2), taraxasterol (3) and β-sitosterol (4). effect of the tested samples 1 and 2 on the viability of RAW macrophage 264.7 were studied. anti-cancer activity was tested on several human cell lines. Anti-inflammatory effect was also screened. Compound 1 had promising cellular cytotoxicity with IC50 60.26µg/mL on HepG2. Compound 2 had a talented cellular cytotoxicity with IC50 50.18 µg/mL on PC3. Both 1 and 2 exerted alike cytotoxicity with IC50 µg/mL 78.53, 78.14 on PC3 and MCF-7 carcinoma cell lines respectively. The treatment of LPS-stimulated macrophage with 2 led to a highly significant inhibition 45.05% in the nitrite concentration in LPS-stimulated macrophage. Compound 1 had a promising cellular cytotoxicity on HepG2, while 2 exhibited an inhibition on chemokine expression in LPS-induced RAW 264.7 macrophages and had talented cellular cytotoxicity on PC3.
Grazing animals cause major alterations to vegetation structure and botanical composition through their selective grazing, trampling and excretal deposition (Hester et al., 2005). Through these effects they modify habitats and thus the populations of invertebrates and other organisms at higher trophic levels. Herbivores are thus key drivers of ecosystem function and nutrient dynamics within grazed plant communities. Changes in grazing intensity and the species mix of grazing livestock can therefore have important implications for resulting biodiversity. Ongoing reform of the European Union Common Agricultural Policy (CAP) will lead to a shift in the way financial support for livestock is distributed and hence to changes in grazing management practices. Farmers will increasingly receive financial support subject to cross-compliance with various environmental conditions and for delivery of specific environmental and social objectives. In some areas, livestock are likely to be increasingly viewed as tools for habitat management rather than solely as producers of food and other commodities.Against this backdrop of policy change the British Society of Animal Science and the British Ecological Society organized a joint symposium at the BSAS Annual Meeting in April 2005 on the links between farm animals and biodiversity. Four papers from this symposium are presented as mini-reviews in the current issue of Animal Science.David Oglethorpe set the policy context in his review of the environmental implications of CAP reform (Oglethorpe, 2005). His paper highlighted the likely changes in the livestock sector that will ensue including a polarization of agriculture into intensive producers versus environmental managers, increasing extensification in the uplands and some substitution of beef with sheep. Jerry Tallowin then presented a review of the impact of grazing management on grassland biodiversity (Tallowin et al., 2005). His paper showed that lenient grazing pressure by cattle in species-rich grassland was sufficient to maintain botanical diversity but did not enhance it over a 5-year period. For species-poor grassland, grazing management could alter sward structure but, in the absence of seed sources, botanical diversity was resistant to change. There is obviously much research still be done in this area to support the development of suitable agri-environment measures under Pillar 2 support mechanisms. David Buckingham went on to consider the extent to which grassland management might influence habitat quality for farmland birds (Buckingham and Peach, 2005). His paper showed that the exacting requirements of declining granivorous birds pose the greatest challenges while the needs of soil invertebrate feeding species are more easily met under agri-environmental schemes. In the final paper by Bruno Martin, the influence of pasture diversity on cheese quality was the theme (Martin et al., 2005). This paper reviewed recent work, primarily from France, which has examined the links between the diet of grazing animals and the sensory characteristics of various Protected Designation of Origin cheeses. The review highlighted the sometimes subtle, but none the less important influence of the grazing environment on food quality.The purpose of the symposium was to draw together animal scientists, conservation biologists, ecologists and socio-economists to consider the changing rôle of farm livestock within the new ‘decoupled’ economic environment. Judging by the popularity of the symposium and the vibrant nature of the discussion that followed each paper, there are plenty of issues still to consider and the hope is that some of the contacts made at the meeting will yield fruitful collaborations in the future.
The lack of invertebrate prey on intensively grazed agricultural grassland can limit reproductive success in farmland birds. The impacts of lenient early season grazing followed by early cessation of grazing on sward structure and invertebrate communities on improved agricultural grassland were tested. The experiment was conducted on 13 pasture fields in south-west England over four successive years. Lenient early season grazing increased total invertebrate abundance by 71% after 4 years, the most responsive groups being Araneae, Auchenorrhyncha, Collembola and Heteroptera. Early cessation of grazing led to increased cover of Holcus lanatus and Agrostis spp. and increased litter accumulation; clover cover and sward structural heterogeneity declined. These sward changes are likely to have reduced agricultural productivity and may have inhibited access to invertebrate prey for foraging birds.
This is the third assessment of the population status of birds in the UK. The listing criteria are based on global conservation status, historical population declines, recent population declines (both in numbers and in geographical range), European conservation status, breeding rarity, localised distribution, and the international importance of populations. For consistency, the criteria follow closely those used by previous reviews, with minor modifications where new information or methods are available. We have assessed the population status of 247 species in the UK: 40 (c. 16%) were placed on the 'Red list', 121 (c. 49%) on the 'Amber list', and 86 (c. 35%) on the 'Green list'. The number of Red-listed species has increased by four, and the number of Amber-listed species by eleven since the previous review in 1996. Nine new species have been added to the Red list because of declines in their breeding populations, while thirty-one species have remained Red listed. Five species have moved from the Red to the Amber list because their populations have more than doubled in the last 25 years.
Population trends of Jay Garrulus glandarius, Magpie Pica pica, Jackdaw Corvus monedula and Carrion Crow Corvus corone were examined over the period 1964–93 using data from the Common Birds Census. Population growth has been highest in the Magpie and Carrion Crow, although both these have shown a reduction in the rate of growth from the late 1970s. Densities of all 4 corvids have increased on farmland, whereas only Magpie and Carrion Crow have increased in woodland. Population trends were associated with farmland type in all the corvids; the strongest increases were on mixed and grazing farms and the smallest on arable farms. There were strong regional differences in trends within woodland and farmland. Our results are discussed in the context of the long%term changes in corvid populations that have been reported since the start of this century.
Between 1992 and 1993 over 600 000 ha of arable farmland in the UK were set aside under a production control mechanism of the Common Agricultural Policy (CAP) of the European Union. One of the management options for this set-aside land was to leave it as an over-winter fallow with a naturally regenerated green cover. This study was designed to test whether such land was used by seed-eating bird species, populations of many of which have undergone recent severe declines. Five out of six declining species recorded in the study were found in significantly greater numbers on this habitat than would be expected if the birds were randomly distributed over the farmland landscape. The results of this study, covering a wide geographical area, reinforce previous findings of the importance of winter food sources, particularly over-winter stubble fields, to declining farmland seed-eaters. Proposed changes to the CAP under Agenda 2000 include the reduction of the obligatory set-aside rate to zero. These results suggest that such a move might be detrimental to populations of declining farmland birds. There is an urgent need for an agri-environment scheme designed to integrate arable production and conservation objectives, which operates in the wider countryside, includes provision for over-winter stubble fields and is available to every arable farmer.
Capsule Extensive 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.
This is the fourth major review of the status of birds occurring in the UK, Channel Islands and Isle of Man.We present Red, Amber and Green lists of conservation concern based on assessments using objective listing criteria and using the most recent data.The listing criteria assess global conservation status, historical population decline, recent population decline (numbers and geographical range), European conservation status, rarity, localised distribution, and international importance of populations. Some changes have been made to the criteria since the last assessment, and the effect of these changes is discussed. Of 246 species assessed, 52 (21.1%) have been placed on the Red list, 126 (51.2%) on the Amber list and 68 (27.6%) on the Green list. Eighteen species have moved onto the Red list since the last assessment in 2002, and six have moved from Red to Amber.
It has been suggested that increased predation rates may rival habitat alteration as a causal agent in farmland bird population declines. Such a view may be over-simplistic, however, as changes in habitat structure may influence habitat selection and foraging efficiency through their influence on perceived and actual predation risk. We review evidence from the literature on the effects of habitat structure on predation risk of foraging and nesting birds and apply these principles to investigate the likely effects on the 20 species that comprise the UK Government's ‘Farmland Bird Index’. Shorter vegetation is likely to enhance foraging efficiency and reduce predation risk (when ground foraging) for 15 of the 20 species. However, within grassland systems longer vegetation is known to enhance food supplies (e.g. Tipulid larvae and voles) of several farmland bird species and so mosaics of short and long vegetation may provide the optimum conditions for most species (e.g. Lapwing Vanellus vanellus, Starling Sturnus vulgaris, Barn Owl Tyto alba). Agricultural intensification has encouraged uniform dense swards, thus reducing habitat diversity, and agri-environment schemes that provide heterogeneous sward structure may thus facilitate farmland bird conservation. Intensification has also resulted in less dense hedgerows; although a reversal of this trend may improve foraging efficiency for many species, it may be detrimental to a smaller number of species that prefer shorter, less dense hedges for nesting. Before these tentative conclusions can be confirmed, more research is required that considers how the effects of habitat structure on individuals is likely to translate into population-level impacts.
Losses of farmland birds from the wider countryside have become a major conservation issue in the UK and Europe. Song thrush Turdus philomelos populations in lowland rural Britain declined by approximately 70% during 1970–95, most severely on intensively managed arable farmland. Comparison between a stable population on mixed farmland and a rapidly declining population on arable farmland revealed fewer nesting attempts each summer by birds in the declining population, and annual productivity was insufficient to maintain local population density. Inadequate food resources were the most plausible cause.
We compared breeding season habitat selection (using radio‐telemetry) and earthworm availability (a major component of summer diet) for song thrushes in the same two farmland populations.
Territory settlement in the mixed farmland landscape involved the selection of field boundaries and woodland and the avoidance of arable crops. Field boundaries and gardens were selected in the arable landscape, while arable break crops and small areas of woodland were avoided.
Habitat selection (intensity of usage) did not change through the breeding season and did not differ between study areas. Scrub, woodland edge, wet ditches and bare soil in gardens were preferred foraging habitats, while cereals were avoided.
Habitat utilization (amount of usage) differed markedly between study areas. Woodland and grassland accounted for 53% of all habitat usage in the mixed farmland landscape compared with just 13% in the arable landscape. Gardens and arable crops were more heavily utilized in the arable landscape, accounting for 58% of all usage compared with 22% in the mixed landscape.
Earthworm availability declined markedly between April and June as surface soils dried out. Lower earthworm availability in the arable landscape was associated with more rapid and pronounced drying of surface soils.
Synthesis and applications. Lack of woodland and grassland, and the faster drying of surface soils in the arable landscape, combined to limit the availability to thrushes of key summer invertebrate prey. Loss of hedgerows, scrub and permanent grassland with livestock, and the wide‐scale installation of under‐field drainage systems, have probably all contributed to the decline of song thrushes on UK arable farmland. New agri‐environment measures may be needed to provide the nesting cover adjacent to invertebrate‐rich damp soils that song thrushes require to sustain annual productivity.
Recently, it has been suggested that habitats for insect herbivores have been too narrowly defined, often on the basis of larval hostplants; in particular, non-consumable resources (called utilities; structural elements) have been ignored. Here, the importance of utility resources for roosting and mate location has been examined in the silver-studded blue butterfly Plebejus argus (L.) (Lycaenidae) on the Great Ormes Head, North Wales, UK. The methods included using dedicated surveys and correspondence analysis applied to behavioural observations in relation to vegetation structure on a transect through a key patch for this metapopulation model species. A substantial and significant bias in roosting (97%) and mating (75%) is found to occur outside hostplant areas on shrubs and rank bunched grasses and forbs. Population density is higher in shrubby areas and shrubs are increasingly occupied during the afternoons and night, during the late flight season and in cloudy, cool and windy weather. These findings suggest that shrubs are a valuable habitat component for this butterfly, at least at this coastal location, and important for their conservation. As scrub growth is inimical to calcicolous grassland, population status will depend on a fine balance between shrub and hostplant cover dependent on grazing and browsing by the indigenous goat, sheep and rabbit populations as well as on controlled cutting and burning. Opportunities exist for increasing population size and distribution on the headland but this will need to be managed carefully. There are also implications for metapopulation dynamics studies; the status of shrubs neighbouring host plant areas switches from that of barriers to resources and refuges.
In the last 50 years, intensification of agricultural grassland management has led to over 97% of all grassland being ‘improved’ in the UK. Despite grassland being an important habitat for birds in Europe, both in terms of area and preference by several species of conservation concern, the impact of grassland intensification on both breeding and wintering birds is poorly understood. This study compared habitat characteristics and bird diversity, in winter, between improved and unimproved lowland grassland in England comprising 44 unimproved fields (350 ha) and 59 improved fields (290 ha) at 7 paired sites. Key habitat differences were found between grassland types. These included, on improved fields, a denser sward, less surface water, more dung flies and more fields with seeding grass. Species that are dependent on soil invertebrates (particularly earthworms) were found to be more numerous on unimproved grassland, whilst generalist insectivores such as corvids were much more numerous on improved grassland. Grassland improvement may have been one important factor behind the recent increases in numbers of some corvid species in the UK.
From a review of the literature, we conclude that the main mechanism by which grazing livestock affect biodiversity in pastures is the creation and maintenance of sward structural heterogeneity, particularly as a result of dietary choice. We identify lack of understanding of the currencies used by animals in their foraging decisions and the spatial scale of these decisions as major constraints to better management. We conclude that there are important differences between domestic grazing animal species in their impact on grazed communities and that these can be related to differences in dental and digestive anatomy, but also, and probably more importantly, to differences in body size. Differences between breeds within species appear to be relatively minor and again largely related to body size. We conclude that there is an urgent need to understand the genetic basis of these differences and also to separate true breed effects from effects of rearing environment. We also review the economic implications of using different animal types and conclude that there is a need for more research integrating these aspects with biodiversity outcomes.
The populations of farmland birds in Europe declined markedly during the last quarter of the 20th century, representing a severe threat to biodiversity. Here, we assess whether declines in the populations and ranges of farmland birds across Europe reflect differences in agricultural intensity, which arise largely through differences in political history. Population and range changes were modelled in terms of a number of indices of agricultural intensity. Population declines and range contractions were significantly greater in countries with more intensive agriculture, and significantly higher in the European Union (EU) than in former communist countries. Cereal yield alone explained over 30% of the variation in population trends. The results suggest that recent trends in agriculture have had deleterious and measurable effects on bird populations on a continental scale. We predict that the introduction of EU agricultural policies into former communist countries hoping to accede to the EU in the near future will result in significant declines in the important bird populations there.
Of the six species of wild geese which winter in Britain in large numbers, five are increasing in number and cause agricultural damage on a local scale. The management of grassland as feeding areas, to attract geese off agricultural land, is widely acknowledged as a potential solution to the problem. Similarly, grassland refuges are commonly established as a means of conserving rare or localised species of geese in Britain. Both require precise management guidelines if grassland areas are to be managed effectively. This paper summarises the information available concerning the management of grassland for wild geese wintering in Britain. We consider criteria for the location of feeding areas and the size of feeding areas required to support given populations of geese on local and national scales. Sward management is considered in terms of species composition and height, the value of fertiliser application and the relative merits of management through livestock grazing or mechanical cutting of grass pastures over the summer. The greatest potential for maximising goose numbers within an area appears to be through manipulation of sward height and fertiliser application. We discuss potential conflicts between managing grassland for geese and for other species and highlight possible directions for future research.
Assessed the effects of farming practices on field choice by wintering birds in an area of mixed farmland in the Vale of Aylesbury, England. Permanent grass fields supported the highest densities of most of the invertebrate-feeding birds and were preferred throughout the winter. Cereal stubble and ley fields supported moderate densities of some birds but were generally avoided. Bare till, winter cereal and oil-seed rape fields were little used. Soil macro-invertebrate densities were highest in permanent grass fields. The biomass of earthworms and other invertebrates was significantly higher in permanent grass than all other field types except ley. The birds' preference for permanent grass fields is probably caused by the high density of food resources. For most species of birds, the likelihood that permanent grass fields would be used was consistently higher where farmyard manure (FYM) was applied frequently and where the grass was long established. Densities of Lumbricidae and Coleoptera were positively correlated with age of grass but not with input of FYM. The greater number of birds observed was possibly a result of increased surface activity of earthworms. -from Author
Three pairs of individually color-banded Choughs (Pyrrhocorax pyrrhocorax) were studied on the island of Islay during the 1992 incubation and nestling periods (21 April-16 June), to investigate the effects of land management factors on adult feeding behavior. The behavior of individual birds was recorded at 1-min intervals. The land utilized by the birds was mapped by farm management unit (compartment) and the use of these, and of 10 biotopes, were recorded together with nine behavioral activities. A total of 15,128 1-min observations was collected on these birds. All three pairs showed distinct selection for grass pasture (either old or new grassland). Over 90% of each pair's time was spent in food collection activity, and invertebrate sampling suggested that the birds were feeding mainly on soil-dwelling tipulid fly larvae (Diptera: Tipulidae). Analyses of compartment agricultural management characteristics data indicated that the small number of preferentially used compartments were those in which (1) management during June-September 1991 produced medium-high grass sward heights, and (2) management between January and May 1992 produced short, open swards. It is suggested that this combination of seasonal management encouraged high numbers of tipulid larvae in the soil during winter and spring and provided optimum foraging conditions for the birds both before and during the incubation and nestling periods. The implications of the findings for pasture management are discussed in relation to their potential to provide relatively simple agricultural management prescriptions to favor Choughs on Islay during the incubation and nestling periods.
This paper reviews recent work carried out by the Institute of Grassland and Environmental Research and collaborating organizations that addresses some of the impacts of grazing management on both species-rich and species-poor lowland neutral grassland. Results indicate that for species-rich grassland, lenient grazing pressure maintained botanical diversity and the abundance of positive indicator species of nature conservation value over a 5-year period and also enhanced faunal diversity and abundance reflecting improvements in spatial, architectural and temporal structure. However, there was no enhancement in positive indicator species and there was also an increase in pernicious weeds suggesting that grazing alone may not suffice to deliver all the biodiversity goals for these grasslands and that additional management interventions may be required. For species-poor grassland, results indicate that distinctive differences in structure can lead to differences in faunal diversity. There is also some tentative evidence that livestock breed may affect invertebrate species assemblages.
On 1 January 2005, the direct support schemes directed at UK livestock farmers as part of the Common Agricultural Policy (CAP) were replaced with a Single Farm Payment, decoupled from production. In practical term, this means that farmers now have freedom of choice over the particular farm enterprises they engage in since their income support is no longer dependent on their type of production. Farmer policy-response will be dependent on their previous dependence on the direct subsidies being replaced, which, as the paper shows, is considerable for UK livestock farmers. The paper suggests a dichotomous shift of farmer objective in the livestock sector in the future, with ‘environmental managers’ and ‘market managers’ focusing on different outputs. The outcome will be a significant down-sizing of the UK livestock sector but with probable net gains to the environment.
1. In the South Downs and South Wessex Downs (southern England), designated an Environmentally Sensitive Area (ESA) in 1987 and 1993, respectively, farmers may undertake to conserve existing areas of downland turf (chalk grassland rich in plants and invertebrates) and to create new areas of grassland out of previously cultivated land (arable reversion), in exchange for annual payments. These areas are subject to strict management prescriptions.
2. Singing skylarks were surveyed on 40 km2 of downland turf, arable reversion, non-ESA grass and arable land between 1994 and 1996 (April–July) in the two ESAs. The emphasis was on two types of arable reversion: permanent grassland sown with agricultural grass species, and chalk downland sown with traditional chalk grass species.
3. The surveys showed that singing skylark density was greater on chalk downland arable reversion than on permanent grassland reversion, in swards above 15 cm in height and in fields without boundary scrub. In general, permanent grassland reversion did not support more skylarks than winter wheat or grass not entered in the ESA schemes; highest densities were in undersown spring barley. Singing skylark density decreased after mowing in May–June in the South Wessex Downs ESA.
4. In 1995 and 1996, a fully randomized experiment was carried out on 12 fields (each c. 5 ha) at Plumpton, Sussex, to verify the survey findings. Six fields were grazed to maintain a sward below 10 cm in height (short-grazed), and the others grazed to maintain a sward between 15 and 25 cm (long-grazed) during the skylark breeding season (April–July).
5. On average, singing skylarks were six times as abundant, and non-singing ones twice as abundant, in experimental long-grazed fields as in short-grazed fields. The total number and number of taxa of chick-food invertebrates were about twice as large on average, and the number of grass seed heads recorded in July was two to 15 times as great, in long-grazed as in short-grazed fields.
6. Grazing-exclusion cages within a randomized block experiment at New Erringham, Sussex, were sampled for invertebrates in mid-May 1995 & 1996. Ungrazed cages (sward up to 40 cm tall) supported over five times as many invertebrates and over three times as many invertebrate taxa as grazed areas (sward <2 cm tall).
7. These results contributed to revised management prescriptions for the South Downs (1997) and South Wessex Downs (1998) ESAs. Prescriptions to encourage taller swards and to prevent mowing during the nesting season in the South Wessex Downs, and removal of the 10-cm limit on sward height, allowance of fertilizer on some arable reversion grassland, and an arable tier encouraging undersown spring cereals and overwinter stubbles in the South Downs, will benefit grassland birds.
In this paper we review the experimental development of agri-environment measures for use on grasslands. Sward structure has been shown to have a strong influence on birds’ ability to forage in grasslands, but the effects of food abundance on foraging behaviour are poorly understood and this hinders development of grassland conservation measures. The experiments described have a dual purpose: to investigate the foraging ecology of birds on grasslands and to test candidate management measures. Most of the work featured focuses on increasing invertebrate food resources during the summer by increasing habitat heterogeneity. We also identify important gaps in the habitats provided by existing or experimental measures, where similar dual-purpose experiments are required.
1. Corn buntings Miliaria calandra have declined steeply in Britain and north-western Europe since the mid-1970s; changes in farming practice are believed to have been partly responsible.
2. We studied nesting corn buntings on the South Downs in west Sussex between 1995 and 1997 to examine the possible effects of agricultural intensification on breeding success. The abundance of invertebrates around individual nests was sampled by sweep-netting in July.
3. Corn buntings provisioning nestlings foraged in grassy margins more than any other habitat relative to their availability within the maximum foraging range. The other habitats used more than expected were spring-sown barley, unintensified grass and set-aside. Those used less than expected included winter-sown wheat and intensively managed grassland. The invertebrates most commonly fed to chicks were more abundant in foraging areas than elsewhere. Their density was negatively correlated with the number of insecticide applications both when cereal fields only were considered and when all foraging habitats were included.
4. The lower the abundance of chick-food invertebrates close to nests, the greater the distance from the nest at which parents foraged, and the longer such trips were in duration. The weights of nestlings, corrected for age using tarsus length, were positively correlated with the abundance of chick-food invertebrates.
5. The probability of nest survival was negatively correlated with the abundance of chick-food invertebrates close to the nest, apparently as a result of an increased risk of predation.
6. Agricultural intensification in Britain, including the increased use of pesticides, has led to a widespread decrease in the availability of chick-food invertebrates on lowland farmland. If our results are typical of corn buntings in an arable environment, this decrease correlates with reduced breeding success. Depending on the mortality rates for fledged chicks and older birds, this reduction may have contributed to the corn buntings' decline and may hamper recovery.
7. Farming practices that increase invertebrate availability ought to benefit breeding corn buntings. Large-scale measures such as set-aside and the spring-sowing of cereals (especially if undersown with grass) depend heavily on overall agricultural policy. Small-scale initiatives might therefore be more feasible; these include the provision of grassy margins or beetle banks and selective spraying of headlands.
Changes in agricultural land-use may have been responsible for contractions in range that have occurred in a number of bird species over the past three decades. This was considered by examining spatial change in the ranges of 21 farmland bird species at the scale of 10 km squares in relation to spatial change in agricultural land-use variables between the late 1960s and the late 1980s in lowland England and Wales. Seven species showed range declines (local extinction) exceeding 5% over this period and analyses focused on these: Grey Partridge Perdix perdix, Lapwing Vanellus vanellus, Turtle Dove Streptopelia turtur, Yellow Wagtail Motacilla flava, Tree Sparrow Passer montanus, Corn Bunting Miliaria calandra and Reed Bunting Emberiza schoeniclus. Individual species loss and change in species richness tended to be related to variables with strong regional trends, reflecting greater losses in western 10 km squares characterized by pastoral agriculture. It is unlikely that many of the variables selected in the regression models are, in themselves, the causal factors behind changes in the ranges of species and changes in species richness. Lapwing was an exception, agricultural variables associated with grassland being consistently selected. Principal Components Analysis (PCA) was applied to the agricultural variables. This identified a major gradient of change in cropping patterns, involving large increases in areas of wheat Triticum spp. and oilseed rape Brassica napus at the expense of barley Hordeum spp., bare fallow and grass. Local extinctions and change in species richness were consistently related to the first PCA axis, showing that local extinctions have occurred most in those squares where there had been relatively little change in crop types. The greater rate of local extinctions in pastoral regions may be associated with a number of factors, including changes in the management of grass and livestock, edge of range effects (where species in less favoured habitats are more likely to become locally extinct) and source-sink effects. These results highlight the need for further research into the effects of agricultural management on birds in pastoral systems. ©2000 Elsevier Science B.V. All rights reserved.
The effects of agricultural intensification on biodiversity in arable systems of western Europe have received a great deal of attention. However, the recent transformation of grassland systems has been just as profound.
In Britain, the management of grassland has changed substantially in the second half of the 20th century. A high proportion of lowland grassland is managed intensively. The major changes include a doubling in the use of inorganic nitrogen, a switch from hay to silage, and increased stocking densities, particularly of sheep. Structurally diverse and species‐rich swards have been largely replaced by relatively dense, fast‐growing and structurally uniform swards, dominated by competitive species.
Most of these changes have reduced the suitability of grassland as feeding and breeding habitat for birds.
The most important direct effects have been deterioration of the sward as nesting and wintering habitat, and loss of seed resources as food. Short uniform swards afford poor shelter and camouflage from predators, whereas increased mowing intensities and trampling by stock will destroy nests and young. Increased frequency of sward defoliation reduces flowering and seed set, and hence food availability for seed‐eating birds.
The indirect effects of intensification of management on birds relate largely to changes in the abundance and availability of invertebrate prey. The effects of management vary with its type, timing and intensity, and with invertebrate ecology and phenology, but, in general, the abundance and diversity of invertebrates declines with reductions in sward diversity and structural complexity.
Low input livestock systems are likely to be central to any future management strategies designed to maintain and restore the ecological diversity of semi‐natural lowland grasslands. Low additions of organic fertilizer benefit some invertebrate prey species, and moderate levels of grazing encourage sward heterogeneity.
There is now a need to improve understanding of how grassland management affects bird population dynamics. Particularly important areas of research include: (i) the interaction between changes in food abundance, due to changes in fertilizer inputs, and food accessibility, due to changes in sward structure; (ii) the interaction between predation rates and management‐related changes in habitat; and (iii) the impact of alternative anti‐helminithic treatments for livestock on invertebrates and birds.
Recent changes in agricultural practice have been hypothesized to affect the abundance and reproductive success of farmland birds. The influence of dairy farming on barn swallows Hirundo rustica was investigated by comparison of their abundance, phenotype and reproduction on the same farms before and immediately after dairy farming ceased, while a control sample of farms without change in farming practice in the same years was used to check for temporal changes unrelated to farming practice.
The abundance of barn swallows decreased significantly when dairy farming ceased, with an average reduction of 48%, while there was no significant difference in the sample of control farms. This was mainly due to a decrease in the abundance of yearling immigrants. The abundance of insect food measured with sweep nets decreased significantly in the absence of cattle, while there was no significant change in the sample of control farms.
The mean phenotypes of adult barn swallows breeding on the same farms with and without dairy farming did not differ significantly for any of the 16 variables measured (11 morphological variables, body mass, parasite load, haematocrit, leucocyte counts, and arrival date), nor were there any significant differences recorded in the sample of control farms.
The mean phenotypes of barn swallow nestlings on the same farms with and without dairy farming differed for tarsus length, body mass, haematocrit, leucocyte concentration and T‐cell mediated immune response, with nestlings being of poorer quality in the absence of cattle. There was no significant differences recorded in the sample of control farms.
Start of reproduction was not delayed in the absence of cattle, but size of first clutches was reduced by the absence of cattle. The frequency of second clutches decreased in the absence of cattle, and laying of second clutches was also delayed. Hatching, fledging and breeding success did not differ between the two types of farming practice. This led to an overall reduction in annual reproductive success in the absence of cattle. None of these significant differences was recorded in the sample of control farms.
These observations suggest that termination of dairy farming reduces local population size, reproductive success and the quality of offspring produced. There is little evidence of the distribution of phenotypes of adult barn swallows being affected by the presence of cattle.
The habitat use and diet of skylarks wintering on lowland farms were studied to assess whether changes in agricultural practice could have reduced their most favoured wintering habitats or foods. Faecal samples were collected and soil seed densities were estimated. Skylarks in 122 cereal stubble fields in Oxfordshire were counted monthly to examine habitat use.
Cereal stubble fields were more likely to be occupied than other crops, and densities of birds in occupied fields were high. Barley stubbles were significantly more likely to be occupied than wheat stubbles. Growing cereals were weakly selected. Sugar beet stubbles held high densities of birds. Rotational set‐aside was occupied more frequently and held higher densities than non‐rotational set‐aside.
Field size affected field occupancy independently of crop type, with larger fields more likely to be occupied. Fields enclosed by hedges or trees tended to be avoided. Cereal and set‐aside fields that were occupied by skylarks in at least 1 month held significantly higher soil seed densities than fields that were not occupied.
Differences in occupancy between crops could be explained by diet. Birds in cereal stubbles fed largely on cereal grain, whereas those in winter cereals fed largely on cereal leaves. Broad‐leaved weed leaves were strongly selected as food in cereal crops and farmland grass fields. In grass fields, the proportion of the diet made up by broad‐leaved weeds was positively correlated with their availability. Broad‐leaved weed seeds did not make up a significant dietary component in any crop.
Our results show that the shift from spring to autumn sowing of cereals has led to a loss of the skylark’s most strongly selected wintering habitat and best food source. In winter cereals and in grass there was a high selectivity for relatively scarce, and probably declining, food resources. Our results suggest that the retention of weed‐rich cereal (particularly barley) and sugar beet stubbles through the winter, particularly in large open blocks, will improve conditions for skylarks in winter. Whole‐field rotational set‐aside, particularly as naturally regenerating cereal stubbles, provides good winter food resources for skylarks.
Over the last 25 years, populations of seed‐eating birds have declined severely over most of western Europe. Local extinctions have occurred in grassland‐dominated areas in western Britain, which may be influenced by loss in habitat diversity and a decline in the amount of arable cultivation.
We used the large‐scale British Breeding Bird Survey of 1998 to investigate the importance of arable habitat within grassland landscapes for 11 common seed‐eating birds and four similar sized insectivores. Generalized linear models were used to model the number of birds recorded in agricultural habitat within survey squares as a function of the amount of arable habitat present.
Numbers of grey partridge Perdix perdix , skylark Alauda arvensis , tree sparrow Passer montanus , corn Miliaria calandra and reed buntings Emberiza schoeniclus , yellowhammer Emberiza citrinella and whitethroat Sylvia communis increased with the amount of arable habitat present in a survey square; the numbers of house sparrow Passer domesticus , four finch species, dunnock Prunella modularis , robin Erithacus rubecula and blackcap Sylvia atricapilla did not.
The positive association between numbers of some species and arable habitat within 1‐km squares was strongest where arable habitat was rare in the surrounding area, and weakest or even reversed when arable habitat was common. These results demonstrate the scale‐dependence of bird–habitat associations in agricultural landscapes, only demonstrable where data are available at fine grain over large geographical areas.
These results support the hypothesis that range contractions (i.e. local extinctions) of some granivorous species have occurred because of contraction in arable cultivation. The loss of arable habitat where it is scarce may be causing declines in some areas, even though intensification of arable management is thought to be the main cause of declines elsewhere. Agri‐environment schemes may need to vary between regions, for example to encourage arable cultivation in pastoral areas.
The importance of structure in grasslands to arthropods is emphasised. Community dynamics below ground are briefly described. The characteristics of stenophagous, polyphagous, predacious and parasitoid arthropods in relation to structure are outlined. Tall grassland supports more species, individuals and a greater diversity of arthropods than short swards, but some species are characteristic of the latter. The classification of structure in grassland is briefly reviewed. Change in grassland structure occurs through the opposing forces of succession and, in most cases, management. The commonest method of management is grazing, which is characterised by selectivity in the foliage eaten, treading of the sward and deposition of dung. Cutting is sudden, but its effects of defoliation are similar to those of grazing. Burning is considered in less detail. Ploughing, rotovating, re-seeding, fertiliser application, translocation and set-aside are generally forms of agricultural or ‘creative’ management. Human treading can have severe effects on invertebrate diversity and abundance. Management interacts with other factors, such as seasonality, timing, topography, site-specific characteristics and connectivity to produce varied effects on arthropods. The various types of management systems, reclamation, maintenance, agricultural, rotational and others are discussed in relation to management plans and objectives in conservation. It is concluded that conservationists need to be more aware of grassland dynamics, that management by reference to past land-use must be tempered by full consideration of ecological factors and conservation aims and that ‘practical’ and ‘theoretical’ conservationists need to interact more effectively.
Almost a third of the bird species designated as Species of European Conservation Concern exploit agricultural grasslands, yet few studies have focused on their use as foraging habitats for birds. This study investigated the influence of variation in sward structure, grassland management and landscape variables on the use of 77 grass fields by 14 field-feeding bird species wintering on lowland mixed farmland in southern England. Multiple logistic regression was used to model the proportion of bird-count visits in which each species was encountered as a function of the recorded habitat variables for each field. Variation in sward height and density were associated with frequency of occurrence for 12 bird species and larger areas of bare earth and occurrence of winter grazing by stock animals were correlated with greater frequency of occurrence by 11 bird species. Two rapidly declining species, skylark (Alauda arvensis) and yellowhammer (Emberiza citrinella), were recorded more frequently on fields with higher numbers of seeding grasses. We suggest that mosaics of fields managed as short-term leys and permanent pastures with low-intensity cattle grazing over the autumn and winter would provide the combination of heterogeneous sward structure, areas of bare earth and presence of some seeding plants necessary to maximise the range of bird species able to use a given area of agriculturally improved grassland throughout the winter.
A field-scale correlative study was used to identify which factors had the greatest influence on the usage of agricultural grassland by foraging birds in the English West Midlands. The study extended previous work by directly comparing a more complete range of lowland grassland management practises, bird species and seasons. Sward structure had more influence on bird usage than botanical composition. Bird species fell into two groups based on their sward structure preferences, which closely reflected where they obtained their food. Species that feed on soil-dwelling invertebrates selected short swards, while species that feed on sward-dwelling invertebrates or seeds selected taller swards with greater spatial heterogeneity. Grazing had a greater influence on grassland usage than sward age and other management practices. Birds mainly responded positively to grazing, especially by cattle. Weed control reduced the usage of grass fields by granivorous birds during summer and winter. Intensive grazing systems create and maintain short, uniform swards that favour bird species foraging for soil-dwelling invertebrates, but not those reliant on seeds or sward-dwelling invertebrates. It is proposed that excessive defoliation of agricultural grasslands (associated with intensive grazing and mowing regimes) impacts granivorous birds by reducing prey abundance. Reductions in grazing intensity and the avoidance of weed control should increase food availability for granivorous and insectivorous birds on grass fields.
Thesis (D. Phil)--University of Oxford, 2001. Includes bibliographical references.
Avermectin residues in the dung from treated livestock are detrimental to dung insects. Rare insects could be put at risk by the use of avermectins, especially those which breed exclusively in the dung of the herbivores on which avermectins are used. Livestock dung is an important feeding habitat for a number of vertebrate species. The potential for direct poisoning of vertebrates through the accumulation of avermectins in the body, after consumption of invertebrates containing residues, would, on present knowledge, appear to be limited, but should not be disregarded. The use of avermectins may also indirectly affect some species of vertebrate by depleting the quality and quantity of important food resources. The effects of any reduction in invertebrate food in livestock dung would be expected to be especially severe if it occurred at critical times for the vertebrates, such as during the breeding season or when newly independent young animals were foraging and fending for themselves. Insects that develop in livestock dung therefore have important, additional roles in the ecology of pasture-lands, other than aiding dung degradation processes. It is essential that these other roles are taken into account when any assessment of the environmental consequences of using avermectins in livestock is being made.
The populations of farmland birds in Europe declined markedly during the last quarter of the 20th century, representing a severe threat to biodiversity. Here, we assess whether declines in the populations and ranges of farmland birds across Europe reflect differences in agricultural intensity, which arise largely through differences in political history. Population and range changes were modelled in terms of a number of indices of agricultural intensity. Population declines and range contractions were significantly greater in countries with more intensive agriculture, and significantly higher in the European Union (EU) than in former communist countries. Cereal yield alone explained over 30% of the variation in population trends. The results suggest that recent trends in agriculture have had deleterious and measurable effects on bird populations on a continental scale. We predict that the introduction of EU agricultural policies into former communist countries hoping to accede to the EU in the near future will result in significant declines in the important bird populations there.
Effects of agriculture on swallows ( ristica). D. Phil. thesis
- K L Evans
Evans, K. L. 2001. Effects of agriculture on swallows (Hirundo
2001. Effects of agriculture on swallows (Hirundo
2001. Effects of agriculture on swallows (
ristica). D. Phil. thesis, Oxford University.
Habitat conservation for insectsa neglected green issue
- R Fry
- D Lonsdale
Fry, R. and Lonsdale, D. 1991. Habitat conservation for insectsa neglected green issue. The amateur entomologist, vol. 21. The
Amateur Entomologist's Society, Orpington, Kent.
Commensal feeding relationships between yellow wagtails Motacilla fl ava and cattle
- H Kallander
Kallander, H. 1993. Commensal feeding relationships between
yellow wagtails Motacilla fl ava and cattle. Ibis 135 : 97-100.
The ecology of linnets Carduelis cannabina on lowland farmland
- D Moorcroft
- J D Wilson
Moorcroft, D. and Wilson, J. D. 2000. The ecology of linnets
Carduelis cannabina on lowland farmland. In Ecology and
conservation of lowland farmland birds (ed. N. J. Aebischer,
A. D. Evans, P. V. Grice and J. A. Vickery), pp. 173-181. British
Ornithologists Union, Tring, UK.