Using an individual-based model to select among alternative foraging strategies of woodpigeons: data support a memory-based model with a flocking mechanism

Population modelling is increasingly recognised as a useful tool for pesticide risk assessment. For vertebrates that may ingest pesticides with their food, such as woodpigeon (Columba palumbus), population models that simulate foraging behaviour explicitly can help predicting both exposure and population-level impact. Optimal foraging theory is often assumed to explain the individual-level decisions driving distributions of individuals in the field, but it may not adequately predict spatial and temporal characteristics of woodpigeon foraging because of the woodpigeons’ excellent memory, ability to fly long distances, and distinctive flocking behaviour. Here we present an individual-based model (IBM) of the woodpigeon. We used the model to predict distributions of foraging woodpigeons that use one of six alternative foraging strategies: optimal foraging, memory-based foraging and random foraging, each with or without flocking mechanisms. We used pattern-oriented modelling to determine which of the foraging strategies is best able to reproduce observed data patterns. Data used for model evaluation were gathered during a long-term woodpigeon study conducted between 1961 and 2004 and a radiotracking study conducted in 2003 and 2004, both in the UK, and are summarised here as three complex patterns: the distributions of foraging birds between vegetation types during the year, the number of fields visited daily by individuals, and the proportion of fields revisited by them on subsequent days. The model with a memory-based foraging strategy and a flocking mechanism was the only one to reproduce these three data patterns, and the optimal foraging model produced poor matches to all of them. The random foraging strategy reproduced two of the three patterns but was not able to guarantee population persistence. We conclude that with the memory-based foraging strategy including a flocking mechanism our model is realistic enough to estimate the potential exposure of woodpigeons to pesticides. We discuss how exposure can be linked to our model, and how the model could be used for risk assessment of pesticides, for example predicting exposure and effects in heterogeneous landscapes planted seasonally with a variety of crops, while accounting for differences in land use between landscapes.

Organic soils promote the efficacy of entomopathogenic nematodes, with different foraging strategies, in the control of a major forest pest: a meta-analysis of field trial data

The large pine weevil, Hylobius abietis, is a serious pest of reforestation in northern Europe. However, weevils developing in stumps of felled trees can be killed by entomopathogenic nematodes applied to soil around the stumps and this method of control has been used at an operational level in the UK and Ireland. We investigated the factors affecting the efficacy of entomopathogenic nematodes in the control of the large pine weevil spanning 10 years of field experiments, by means of a meta-analysis of published studies and previously unpublished data. We investigated two species with different foraging strategies, the ‘ambusher’ Steinernema carpocapsae, the species most often used at an operational level, and the ‘cruiser’ Heterorhabditis downesi. Efficacy was measured both by percentage reduction in numbers of adults emerging relative to untreated controls and by percentage parasitism of developing weevils in the stump. Both measures were significantly higher with H. downesi compared to S. carpocapsae. General linear models were constructed for each nematode species separately, using substrate type (peat versus mineral soil) and tree species (pine versus spruce) as fixed factors, weevil abundance (from the mean of untreated stumps) as a covariate and percentage reduction or percentage parasitism as the response variable. For both nematode species, the most significant and parsimonious models showed that substrate type was consistently, but not always, the most significant variable, whether replicates were at a site or stump level, and that peaty soils significantly promote the efficacy of both species. Efficacy, in terms of percentage parasitism, was not density dependent.

Foraging strategies of natural enemies of the peach-potato aphid Myzus persicae

The foraging strategies of two natural enemies of the peach-potato aphid Myzus persicae: the seven-spot ladybird Coccinella septempunctata and the parasitoid wasp Diaeretiella rapae, were investigated. Specifically the roles of plant semiochemicals in the location of plants infested with M. persicae by these natural enemies were examined. I investigated the olfactory responses of female C. septempunctata to volatiles collected from M. persicae and four Brassica cultivars; Brassica rapa, B. juncea, B. napus cultivar ‘Apex’ and B. napus cultivar ‘Courage’ and wild-type Arabidopsis thaliana that were: undamaged, previously infested by M. persicae and infested with M. persicae. C. septempunctata showed no attraction to volatiles from M. persicae alone. C. septempunctata significantly changed its searching behaviour in response to plant volatiles from B. rapa, B. napus cv. ‘Apex’ and Arabidopsis infested with M. persicae. C. septempunctata was also found to display a significant turning bias when foraging on a branching horizontal wire stem. A model was developed to investigate how turning biases affect the foraging efficiency of C. septempunctata in dichotomous branched environments. Simulations using this model indicated that turning biases could potentially increase searching efficiency. D. rapae showed a significant preference for volatiles from M. persicae infested wild-type Arabidopsis but no preference to volatiles from M. persicae alone or M. persicae honeydew. Volatile emissions by Arabidopsis were shown to be localised to the area of aphid-infestation rather than systemic. Using gas chromatography plants infested with M. persicae were shown to emit a quantitatively different volatile blend than undamaged plants. In experiments with jasmonate mutants of Arabidopsis the jasmonate (octadecanoid) wound response pathway was implicated as being important for the production of M. persicae induced volatiles, attractive to D. rapae. Other wound response pathways were also found to be involved in the production of the full blend of M. persicae induced volatiles.

Optimal foraging when regulating intake of multiple nutrients

There is growing evidence that, rather than maximizing energy intake subject to constraints, many animals attempt to regulate intake of multiple nutrients independently. In the complex diets of animals such as herbivores, the consumption of nutritionally imbalanced foods is sometimes inevitable, forcing trade-offs between eating too much of nutrients present in the foods in relative excess against too little of those in deficit. Such situations are not adequately represented in existing formulations of foraging theory. Here we provide the necessary theory to fit this case, using an approach that combines state-space models of nutrition with Tilman's models of resource exploitation (Tilman 1982, Resource Competition and Community Structure, Princeton: Princeton University Press). Our approach was to construct a smooth fitness landscape over nutrient space, centred on a 'target' intake at which no fitness cost is incurred, and this leads to a natural classification of the simple possible fitness landscapes based on Taylor series approximations of landscape shape. We next examined how needs for multiple nutrients can be assessed experimentally using direct measures of animal performance as the common currency, so that the nutritional strategies of animals can be mapped on to the performance surface, including the position of regulated points of intake and points of nutrient balance when fed suboptimal foods. We surveyed published data and conducted an experiment to map out the performance landscape of a generalist leaf-feeding caterpillar, Spodoptera littoralis. (C) 2004 Tire Association for the Study of Animal Behaviour. Poblished by Elsevier Ltd. All rights reserved.

Contemporary social variations in household water use, management strategies and awareness under conditions of 'water stress': the case of Greater Amman Jordan

One of the distinctive characteristics of the water supply system of Greater Amman, the capital of Jordan, is that it has been based on a regime of rationing since 1987, with households receiving water once a week for various durations. This reflects the fact that while Amman's recent growth has been phenomenal, Jordan is one of the ten most water-scarce nations on earth. Amman is highly polarised socio-economically, and by means of household surveys conducted in both high- and low-income divisions of the city, the aim has been to provide detailed empirical evidence concerning the storage and use if water, the strategies used by households to manage water and overall satisfactions with water supply issues, looking specifically at issues of social equity. The analysis demonstrates the social costs of water rationing and consequent household management to be high, as well as emphasising that issues of water quality are of central importance to all consumers.

Simulating metals and mine discharges in river basins using a new integrated catchment model for metals: pollution impacts and restoration strategies in the Aries-Mures river system in Transylvania, Romania

The INtegrated CAtchment (INCA) model has been developed to simulate the impact of mine discharges on river systems. The model accounts for the key kinetic chemical processes operating as well as the dilution, mixing and redistribution of pollutants in rivers downstream of mine discharges or acid rock drainage sites. The model is dynamic and simulates the day-to-day behaviour of hydrology and eight metals (cadmium, mercury, copper, zinc, lead, arsenic, manganese and chromium) as well as cyanide and ammonia. The model is semi-distributed and can simulate catchments, sub-catchment and in-stream river behaviour. The model has been applied to the Roia Montan Mine in Transylvania, Romania, and used to assess the impacts of old mine adits on the local catchments as well as on the downstream Aries and Mures river system. The question of mine restoration is investigated and a set of clean-up scenarios investigated. It is shown that the planned restoration will generate a much improved water quality from the mine and also alleviate the metal pollution of the river system.

Inclusion, social networks and resilience: strategies, practices and outcomes for disabled children and their families

This paper explores the strategies of service providers and the benefits reported by disabled children and their parents/carers in three Children's Fund programmes in England. Based on National Evaluation of the Children's Fund research, we discuss how different understandings of ‘inclusion’ informed the diverse strategies and approaches service providers adopted. While disabled children and families perceived the benefits of services predominantly in terms of building individual children's resilience and social networks, the paper highlights the need for holistic approaches which have a broad view of inclusion, support children's networks and tackle disabling barriers within all the spheres of children's lives.

Remaking place and securitising space: Urban regeneration and the strategies, tactics and practices of policing in the UK

Urban regeneration programmes in the UK over the past 20 years have increasingly focused on attracting investors, middle-class shoppers and visitors by transforming places and creating new consumption spaces. Ensuring that places are safe and are seen to be safe has taken on greater salience as these flows of income are easily disrupted by changing perceptions of fear and the threat of crime. At the same time, new technologies and policing strategies and tactics have been adopted in a number of regeneration areas which seek to establish control over these new urban spaces. Policing space is increasingly about controlling human actions through design, surveillance technologies and codes of conduct and enforcement. Regeneration agencies and the police now work in partnerships to develop their strategies. At its most extreme, this can lead to the creation of zero-tolerance, or what Smith terms 'revanchist', measures aimed at particular social groups in an effort to sanitise space in the interests of capital accumulation. This paper, drawing on an examination of regeneration practices and processes in one of the UK's fastest-growing urban areas, Reading in Berkshire, assesses policing strategies and tactics in the wake of a major regeneration programme. It documents and discusses the discourses of regeneration that have developed in the town and the ways in which new urban spaces have been secured. It argues that, whilst security concerns have become embedded in institutional discourses and practices, the implementation of security measures has been mediated, in part, by the local socio-political relations in and through which they have been developed.

Impacts of climate change on in-stream nitrogen in a lowland chalk stream: An appraisal of adaptation strategies

The impacts of climate change on nitrogen (N) in a lowland chalk stream are investigated using a dynamic modelling approach. The INCA-N model is used to simulate transient daily hydrology and water quality in the River Kennet using temperature and precipitation scenarios downscaled from the General Circulation Model (GCM) output for the period 1961-2100. The three GCMs (CGCM2, CSIRO and HadCM3) yield very different river flow regimes with the latter projecting significant periods of drought in the second half of the 21st century. Stream-water N concentrations increase over time as higher temperatures enhance N release from the soil, and lower river flows reduce the dilution capacity of the river. Particular problems are shown to occur following severe droughts when N mineralization is high and the subsequent breaking of the drought releases high nitrate loads into the river system. Possible strategies for reducing climate-driven N loads are explored using INCA-N. The measures include land use change or fertiliser reduction, reduction in atmospheric nitrate and ammonium deposition, and the introduction of water meadows or connected wetlands adjacent to the river. The most effective strategy is to change land use or reduce fertiliser use, followed by water meadow creation, and atmospheric pollution controls. Finally, a combined approach involving all three strategies is investigated and shown to reduce in-stream nitrate concentrations to those pre-1950s even under climate change. (c) 2006 Elsevier B.V. All rights reserved.

Identifying appropriate construction procurement strategies

The origins of the various procurement methods in construction are considered, followed by a discussion of the circumstances for which each procurement system is best suited. The likely future development sin management-based methods are discussed in the context of current research, showing that co-ordination of trade and specialist contractors , more flexible contracting, constructive conflict management and a potential polarization of views about project management in the industry are likely.