Philip V. Grice

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

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

The protozoan parasite Trichomonas gallinae causes adult and nestling mortality in a declining population of European Turtle Doves, Streptopelia turtur

Studies incorporating the ecology of clinical and sub-clinical disease in wild populations of conservation concern are rare. Here we examine sub-clinical infection by Trichomonas gallinae in a declining population of free-living European Turtle Doves and suggest caseous lesions cause mortality in adults and nestlings through subsequent starvation and/or suffocation. We found a 100% infection rate by T. gallinae in adult and nestling Turtle Doves (n = 25) and observed clinical signs in three adults and four nestlings (28%). Adults with clinical signs displayed no differences in any skeletal measures of size but had a mean 3.7% reduction in wing length, with no overlap compared to those without clinical signs. We also identified T. gallinae as the suggested cause of mortality in one Red-legged Partridge although disease presentation was different. A minimum of four strains of T. gallinae, characterized at the ITS/5.8S/ITS2 ribosomal region, were isolated from Turtle Doves. However, all birds with clinical signs (Turtle Doves and the Red-legged Partridge) carried a single strain of T. gallinae, suggesting that parasite spill over between Columbidae and Galliformes is a possibility that should be further investigated. Overall, we highlight the importance of monitoring populations for sub-clinical infection rather than just clinical disease.

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

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

Influence of agri-environment scheme options on territory settlement by Yellowhammer (Emberiza citronella) and Corn Bunting (Emberiza calandra)

Conserving farmland birds is a key objective for agri-environment schemes (AES) across Europe, with a number of management options aimed at providing invertebrate food and nesting habitats. We analysed territory settlement by two widespread but declining farmland buntings with contrasting nesting requirements: the Yellowhammer Emberiza citrinella, a boundary-nesting species, and the Corn Bunting Emberiza calandra, a ground-nesting species. The study was conducted on farms participating in the English Higher Level Stewardship scheme to test whether territory settlement is influenced by the provision of key arable AES options. Both species settled preferentially in localities containing sown arable field margins, while Corn Bunting also settled in localities containing nectar flower mixtures. These preferences are likely to reflect foraging rather than nesting habitat requirements. Yellowhammer selected territories containing hedgerows under AES management, which are nesting rather than foraging habitat but may also provide food. Uptake by land owners of several AES options likely to provide limiting resources for farmland birds was very low, and because uptake at the landscape scale is also low, wider-scale population level benefits are likely to be constrained. However, this is one of few studies demonstrating selection of widely applied arable AES options by breeding farmland birds.ZusammenfassungUmweltschutzprogramme in der Landwirtschaft und ihr Einfluss auf die Besiedlung durch Goldammern (Emberiza citronella) and Grauammern (Emberiza calandra) Die Erhaltung der Vogelwelt von Agrarlandschaften ist überall in Europa ein primäres Ziel landwirtschaftlicher Umweltschutzprogramme und beinhaltet eine ganze Reihe von Management-Optionen zur Erhaltung von Nistarealen und auch von Wirbellosen als Futterquelle. Wir analysierten die Besiedelung von Farmland bei zwei weit verbreiteten, jedoch rückläufigen Ammernarten mit unterschiedlichen Nestbau-Anforderungen: die Goldammer, eine Art, die an Waldrändern und im Gebüsch nistet, und die bodenbrütende Grauammer. Unsere Untersuchung wurde auf Farmen durchgeführt, die am English Higher Level Stewardship-Programm teilnehmen. In diesem Programm soll festgestellt werden, ob eine Besiedlung durch die Vögel von der Umsetzung spezieller landwirtschaftlicher Umweltschutzprogramme beeinflusst wird. Beide Ammernarten siedelten sich bevorzugt in solchen Arealen an, in denen die Ackerraine eingesät worden waren, während die Grauammern auch in Arealen mit einer Mischung unterschiedlicher Blütenpflanzen siedelten. Diese Vorlieben spiegeln aber wohl eher Anforderungen an die Nahrungssuche als an Nistareale wider. Die Goldammern bevorzugten Flächen mit Hecken, die im Rahmen von Umweltschutzprogrammen angelegt worden waren und sich eher als Nistgebiete eignen, aber für die Nahrungssuche ebenfalls gut sind. Nur sehr wenige Landbesitzer in der Landwirtschaft waren bereit, ausgewählte Schutzprogramme umzusetzen, die Feldvögeln begrenzte Ressourcen geboten hätten, und da die Bereitschaft auch auf Landschaftsebene recht niedrig ist, sind positive Auswirkungen für größere Populationen vermutlich eher begrenzt. Nichtsdestotrotz ist dies eine von nur wenigen Untersuchungen, die zeigt, dass Feldvögel bestimmte, weit verbreitete Umweltschutzmaßnahmen im landwirtschaftlichen Bereich für die Besiedlung bevorzugen.

The impact of changing habitat availability on population trends of woodland birds associated with early successional plantation woodland

Capsule Trends in young woodland availability influenced population trends and abundance of Tree Pipit and Lesser Redpoll, but not 10-km square occupancy. Aims To investigate whether changes in availability of young woodland could have driven population change, and trends in abundance and occupancy, of declining Tree Pipit and Lesser Redpoll populations in Britain. Methods Modelling approaches used annual population indices and woodland planting statistics. Abundance and occupancy change between two bird atlases were examined in relation to changes in woodland availability from two woodland inventories. Results English declines were strongly associated with decreases in young coniferous woodland availability and less strongly with increases in young broadleaved woodland. Abundance was related to the area of young woodland in corresponding 10-km squares. Young woodland availability declined between forest inventories and species occupancy maintained in 10-km squares with more young woodland; however squares that showed retention or increases in occupancy showed higher reductions in woodland. Conclusion We suggest declining availability of young coniferous woodland contributed to Tree Pipit and Lesser Redpoll population trends in England. Although likely to be the case in Scotland and Wales, the lack of sufficient temporal data inhibited our ability to test this properly. This work suggests that woodland availability was not the primary driver of Tree Pipit or Lesser Redpoll population trends.

Designing lowland landscapes for farmland birds: scenario testing with GIS

Habitat association models have recently been constructed for two farmland bird species: the skylark (Alauda arvensis) and the yellowhammer (Emberiza citrinella). These models are based on a number of predictor variables which describe habitat variation measured at several farms in Oxfordshire, UK. They explain a high proportion of the variation in territory density and species occurrence for these two species and have been incorporated within a GIS. This system allows the user to manipulate the landscape, both structurally (by altering and/or removing boundaries) and agronomically (by changing the nature and timing of the cropping). The bird models are then reapplied to this changed landscape and the potential impact on the two species can be visualised in the form of a map. By comparing this to the baseline situation the degree and direction of change can be seen. As long as the assumptions and limitations of the underlying models are clearly understood, the GIS visualisation allows the ecological knowledge encapsulated in the models to be presented in a powerful and intuitive manner. The result is a system, which can be used for advisory work and policy advocacy for farmland birds.

Post-fledging habitat selection in a rapidly declining farmland bird, the European Turtle Dove Streptopelia turtur

Post-fledging survival plays a vital role in the dynamics of bird populations and yet is the least studied avian life-stage. Habitat requirements post-fledging may have important implications for behaviour and survival, especially for declining populations in landscapes that have undergone wide-scale anthropogenic modification, resulting in an altered distribution and composition of habitats. The European Turtle Dove is a widespread but rapidly declining species both within the UK and across Europe. Reduced seed food availability is thought to influence breeding success of this species, but it is not known whether post-fledging survival may also be influenced by seed availability. Here, we use leg-ring radio-tag attachments to monitor post-fledging survival and movements in 15 Turtle Dove nestlings from eight nests monitored during 2014 as part of a wider autecological study. Fledglings remained in close proximity to their nest for three weeks post-tagging, spending more than half their time in the immediate vicinity (within ∼ 20 m) of the nest. 95% of foraging trips during this period were within 329 m of the nest and fledglings selected seed-rich habitat (semi-natural grassland, low-intensity grazing, fallow and quarries). Fledglings that were heavier and in better body condition at seven days old were more likely to survive for 30 days post-fledging, and the proportion of available seed-rich habitat was a strong predictor of nestling weight and condition at seven days old. Whilst our sample size is modest, this study highlights the crucial role of food availability in juvenile survival, both while adults are feeding nestlings, and to recently fledged young, and the potential for agri-environment schemes providing foraging and nesting habitats in close proximity to provide important benefits.

Foraging habitat selection by breeding Common Kestrels Falco tinnunculus on lowland farmland in England

Capsule Breeding Common Kestrels prefer to forage over recently cut grass than all other habitat types on farmland. Aims To identify foraging habitat and prey of Common Kestrels during the breeding season. Methods We observed seven pairs of Common Kestrels during the breeding season over three years, using fixed vantage point observations. We recorded foraging attempts, and habitat and prey data for where the birds chose to forage. Compositional Analysis was used to establish use of each habitat category relative to that habitat’s availability within the Kestrels’ observed foraging ranges. Results We found that Kestrels select habitats non-randomly, with cut grass (le;5cm, all cut less than two weeks previously) being the most used relative to availability. Prey taken varied with grass height: the ratio of mammals to invertebrates was greater on cut grass (4.36 mammals: 1 invertebrate) than on longer, uncut grass swards (1.73 mammals: 1 invertebrate). Conclusion Our results highlight the importance of areas of long and short grass in close juxtaposition, to provide conditions suitable for prey and access to them, respectively. The creation and maintenance of such small-scale habitat heterogeneity will be the key to maximizing the benefits of English agri-environment schemes for Common Kestrels.

Influence of crop type and Agri-Environment management on the use of over-winter stubbles by farmland birds in England

Capsule Bunting densities decreased in winter wheat stubbles between November/December and January/February, but not in spring barley stubbles. Aims We investigated bird use and vegetation in relation to Agri-Environment Scheme over-winter stubble type and preceding crop. Methods We surveyed 15–17 fields each of: ‘standard’ Agri-Environment Scheme stubble on Entry Level Stewardship farms (EF6); ‘standard’ Agri-Environment Scheme stubble on Higher Level Stewardship farms (HF6); stubble preceded by low-input cereal (HF15); extended over-winter stubble (EF22) and non-Agri-Environment Scheme stubble in November/December 2011 and January/February 2012. Stubbles were preceded by spring barley or winter wheat crops. Results Previous cropping and time of year were the main factors influencing bird densities: bunting densities declined in winter wheat stubbles between surveys, but not in spring barley stubbles. Conclusion The main factor limiting the ability of over-winter stubbles to reverse national population trends of farmland birds is likely to be scale of provision. However, this study suggests that selecting spring barley crops to leave as over-winter stubbles may benefit granivorous farmland birds.

High rates of infection by blood parasites during the nestling phase in UK Columbids with notes on ecological associations

Studies of blood parasite infection in nestling birds rarely find a high prevalence of infection. This is likely due to a combination of short nestling periods (limiting the age at which nestlings can be sampled) and long parasite prepatent periods before gametocytes can be detected in peripheral blood. Here we examine rates of blood parasite infection in nestlings from three Columbid species in the UK. We use this system to address two key hypotheses in the epidemiology of avian haemoparasites: first, that nestlings in open nests have a higher prevalence of infection; and second, that nestlings sampled at 14 days old have a higher apparent infection rate than those sampled at 7 days old. Open-nesting individuals had a 54% infection rate compared with 25% for box-nesters, probably due to an increased exposure of open-nesting species to dipteran vectors. Nestlings sampled at 14 days had a 68% infection rate compared with 32% in nestlings sampled at 7 days, suggesting that rates of infection in the nest are high. Further work should examine nestlings post-fledging to identify rates of successful parasite infection (as opposed to abortive development within a dead-end host) as well as impacts on host post-fledging survival and behaviour.