2,322 research outputs found

    Modeling the Wintering Habitat Distribution of Oriental Honey Buzzards in West Java Indonesia with Satellite Tracking Data Using Logistic Regression

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    Oriental honey buzzards (OHBs, Pernis ptilorhynchus) are one of migratory raptor from Japan to Indonesia which is widely recognized as indicator species reflecting the conditions of their habitat. Since 2003, OHBs have been satellite-tracked in their wintering grounds in Indonesia. Less information available on wintering areas in the west Java, which hampers the OHB conservation efforts. This paper proposes a new approach for predicting the probability models of the wintering habitat distribution of OHBs with the presence data derived from satellite tracking using logistic regression analysis coupled with RAMAS GIS. This spatial model was locally constructed from the data concerning Talaga Bodas and its surrounding areas and extrapolated for the entire West Java region. The best predicted probability model successfully characterized the distribution of the OHB wintering habitat using slope (25–40%), elevation (0–300 m and >1,000 m), and land cover (forest, paddy field, and water body). The extrapolation model generated potential areas of the wintering habitat distribution covering an area of 3013.13 km2 (8.11% of West Java). These areas were predominantly located outside the protected areas (94.04%). The modeling approach proposed herein may be used to study other migratory species that are tracked using satellite or other navigation technologies

    The effects of climate change on the global migration of birds

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    Migration is one of the most spectacular wonders of the natural world but is increasingly threatened by large-scale environmental change. Migrants are key components of biological systems at higher latitudes, where the magnitude and velocity of climate change is most pronounced. In this thesis, I consider how the distribution of migratory species may change in the future, across the globe, in response to environmental change. Using global data on avian species distributions, the environmental and biological factors that affect migratory species richness were investigated. The cost of migration distance between breeding and non-breeding areas, and resident species richness were two important determinants of migrant species richness in a given location. Species distribution models (SDMs) were used to relate migratory species occurrence in breeding and non-breeding seasons to contemporary climatic variables. The importance of climatic variables for predicting migrant species’ occupancy depended on season (breeding or non-breeding). Whilst most SDMs focus on individual species breeding ranges, and model within the occupied realm, this can be problematic for migratory species that frequently use multiple realms, especially if trying to project newly suitable areas in future. Here, I developed a novel method to assess climatic suitability for migratory species globally, within species migration flyways. Selecting absence data to condition SDMs for species occurring across multiple realms can be problematic, as regions distant from the range may be suitable but unoccupied. To minimise this issue, I developed a modelling approach that selected absences preferentially from closer to a species distribution, using a distance weighting function; compared to other methods, this improved model performance on withheld test data. Using this approach, I projected the potential future breeding and non-breeding ranges of all global terrestrial long-distance migrants under climate change. Migrant breeding ranges were projected to shift poleward, but non-breeding range shift projections are less consistent in direction. To date, predictions of migratory changes under future climate scenarios have usually estimated a single distance between breeding and non-breeding range centroids. However, this approach ignores the variation in migratory movements within species. I developed a method to estimate the range of potential migration distances for individual populations, both now and in the future, which agreed well with recovery data for a well-recorded European trans-Saharan migrant. This approach projected longer median migratory distances in the future for many species. This thesis highlights the importance of climate for migratory species, and suggests that the observed general decline in many long-distance migratory species may be exacerbated by ongoing climate change

    Adaptive management of Ramsar wetlands

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    Abstract The Macquarie Marshes are one of Australia’s iconic wetlands, recognised for their international importance, providing habitat for some of the continent’s more important waterbird breeding sites as well as complex and extensive flood-dependent vegetation communities. Part of the area is recognised as a wetland of international importance, under the Ramsar Convention. River regulation has affected their resilience, which may increase with climate change. Counteracting these impacts, the increased amount of environmental flow provided to the wetland through the buy-back and increased wildlife allocation have redressed some of the impacts of river regulation. This project assists in the development of an adaptive management framework for this Ramsar-listed wetland. It brings together current management and available science to provide an informed hierarchy of objectives that incorporates climate change adaptation and assists transparent management. The project adopts a generic approach allowing the framework to be transferred to other wetlands, including Ramsar-listed wetlands, supplied by rivers ranging from highly regulated to free flowing. The integration of management with science allows key indicators to be monitored that will inform management and promote increasingly informed decisions. The project involved a multi-disciplinary team of scientists and managers working on one of the more difficult challenges for Australia, exacerbated by increasing impacts of climate change on flows and inundation patterns

    Connectivity modelling for a species-driven nature recovery network in Oxfordshire

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    The development of England’s new Nature Recovery Network has been piloted in several counties in the country, but few have systematically mapped connectivity based on species dispersal. This study proposes and evaluates a novel modelling framework that integrates various layers of species information into a spatial conservation prioritization analysis. It aims to strategically identify optimal zones for nature recovery that can maximize species connectivity in Oxfordshire, using bats as a focal species. The framework was able to not only identify key landscape corridors but also stepping stone habitats for bats and emphasized how well-placed, small-scale green and blue infrastructure, such as hedgerows and ponds, can be just as effective as larger reserves. It also found that the current coverage of protected areas may not adequately be protecting woodland habitat needed for connectivity. Next steps for Oxfordshire’s NRN should scale up the application of this connectivity framework to address these areas of priority in the landscape

    Beyond Site-Specific Criteria: Conservation of Migratory Birds and Their Habitats from a Network Perspective

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    Many populations of birds depend on networks of sites to survive. Sufficient connectivity that allows movement between the sites throughout the year is a critical requirement. We found that existing international frameworks and policies for identifying sites important for bird conservation focus more at the level of the individual site than on the site network and its connectivity. Only 21% of site criteria acknowledge the importance of movement networks for birds, and such network criteria were mostly (67%) qualitative. We suggest a three-step quantitative approach for informing conservation about the connectivity of bird movements (especially when migrating) from a network perspective, by reviewing current scientific knowledge. The first step is to construct a bird movement network by identifying sites frequently used by birds as ‘nodes’, and then define ‘edges’ from the probability of non-stop flight between each pair of nodes. The second step is to quantify network connectivity, i.e., the extent to which the site network facilitates bird movements. The last step is to assess the importance of each site from its contribution to network connectivity. This approach can serve as a tool for comprehensive and dynamic monitoring of the robustness of site networks during global change

    Beyond Site-Specific Criteria: Conservation of Migratory Birds and Their Habitats from a Network Perspective

    Get PDF
    Many populations of birds depend on networks of sites to survive. Sufficient connectivity that allows movement between the sites throughout the year is a critical requirement. We found that existing international frameworks and policies for identifying sites important for bird conservation focus more at the level of the individual site than on the site network and its connectivity. Only 21% of site criteria acknowledge the importance of movement networks for birds, and such network criteria were mostly (67%) qualitative. We suggest a three-step quantitative approach for informing conservation about the connectivity of bird movements (especially when migrating) from a network perspective, by reviewing current scientific knowledge. The first step is to construct a bird movement network by identifying sites frequently used by birds as ‘nodes’, and then define ‘edges’ from the probability of non-stop flight between each pair of nodes. The second step is to quantify network connectivity, i.e., the extent to which the site network facilitates bird movements. The last step is to assess the importance of each site from its contribution to network connectivity. This approach can serve as a tool for comprehensive and dynamic monitoring of the robustness of site networks during global change

    WILD BIRDS AND EMERGING DISEASES: MODELING AVIAN INFLUENZA TRANSMISSION RISK BETWEEN DOMESTIC AND WILD BIRDS IN CHINA

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    Emerging infectious diseases in wildlife have become a growing concern to human health and biological systems with more than 75 percent of known emerging pathogens being transmissible from animals to humans. Highly pathogenic avian influenza (HPAI) H5N1 has caused major global concern over a potential pandemic and since its emergence in 1996 has become the longest persisting HPAI virus in history. HPAI viruses are generally restricted to domestic poultry populations, however, their origins are found in wild bird reservoirs (Anatidae waterfowl) in a low-pathogenic or non-lethal form. Understanding the spatial and temporal interface between wild and domestic populations is fundamental to taking action against the virus, yet this information is lacking. My dissertation takes two approaches to increase our understanding of wild bird and H5N1 transmission. The first includes a field component to track the migratory patterns of bar-headed geese (Anser indicus) and ruddy shelduck (Tadorna ferruginea) from the large H5N1 outbreak at Qinghai Lake, China. The satellite telemetry study revealed a new migratory connection between Qinghai Lake and outbreak regions in Mongolia, and provided ecological data that supplements phylogenetic analyses of virus movement. The second component of my dissertation research took a modeling approach to identify areas of high transmission risk between domestic poultry and wild waterfowl in China, the epicenter of H5N1. This effort required the development of spatial models for both the poultry and wild waterfowl species of China. Using multivariate regression and AIC to determine statistical relationships between poultry census data and remotely-sensed environmental predictors, I generated spatially explicit distribution models for China's three main poultry species: chickens, ducks, and geese. I then developed spatially explicit breeding and wintering season models of presence-absence, abundance, and H5N1 prevalence for each of China's 42 Anatidae waterfowl species. The poultry and waterfowl datasets were used as the main inputs for the transmission risk models. Distinct patterns in both the spatial and temporal distributions of H5N1 risk was observed in the model predictions. All models included estimates of uncertainty, and sensitivity analyses were performed for the risk models

    Determinants of nesting and nest success in saltmarsh breeding Common Redshank, Tringa totanus, in North West England

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    Abstract Breeding populations of Common Redshank, Tringa totanus, Redshank hereafter, on British saltmarshes halved between 1985 and 2011, with the North West of England experiencing some of the largest losses. Understanding the drivers of these declines and exploring conservation management options to redress losses is the primary focus of this thesis. I first evaluated the reliability of a standardised survey method (SSM) for estimating Redshank nesting density on saltmarshes. This involved multiple walked censuses on four saltmarshes in North West England. Estimates of peak nesting density derived from the SSM were compared to detailed nest monitoring information gathered at the same sites. The SSM was found to overestimate nesting density by 42% across the study sites. Reasons for this discrepancy were considered to be, (i) the presence of non-breeding birds, (ii) differing causes of nest failure across different habitats and areas, and (iii) geographical variation in, and temporal changes to, nesting phenology, the latter likely related to ongoing climate change. I then examined the temporal and spatial distribution of wildfowl and livestock, and their effect on saltmarsh vegetation height in relation to Redshank nesting attempts. To do this, I used observational and experimental exclusion approaches on Banks Marsh, part of the Ribble Estuary National Nature Reserve, over a 30-month period. Cattle usage was variable spatially across the site with higher usage of the inner (landward) marsh compared to the outer marsh, but with a consistency of areas with greatest and least use between years. The number of nests trampled by cattle was relatively low (15%), occurring in areas of shorter vegetation and higher cattle use. Winter wildfowl herbivory played a crucial role in reducing saltmarsh vegetation height, with wildfowl grazed vegetation typically one third of the height of ungrazed vegetation (wildfowl excluded) during the peak Redshank nesting period. Redshank selected nest sites in taller vegetation and successful nests were in significantly taller vegetation than nests that failed. Using the data collected from Banks Marsh, I developed a logistic regression model based on key biotic (cattle, duck, and goose herbivory) and abiotic variables, including elevation above sea level, to predict where Redshank nest on saltmarshes. Winter grazing by Eurasian Wigeon, Mareca penelope, had a strong negative impact on Redshank nesting, whereas light, late summer grazing by cattle had a positive impact. A modelled reduction in Wigeon use whilst maintaining light cattle grazing optimised the availability of suitable nesting habitat. Under such a regime, Redshank numbers were projected to remain relatively unchanged in future under a scenario of a sea level rise of 0.25m. Under other scenarios of sea-level rise and management, Redshank populations were much reduced. The model developed provided a framework for simulating potential ‘trade-offs’ between wildfowl and breeding wader populations, where a conservation conflict could occur, and for long-term conservation management planning for future climate change impacts. Finally, I investigated the effects of livestock and wildfowl herbivory, flooding, and predation on Redshank nest survival. I analysed self-collected and long-term nest-record data from Banks Marsh between 1969 and 2018, using Program MARK. Redshank nest survival was most strongly negatively affected by dramatic increases in winter duck herbivory. Increasing cattle grazing intensity during the Redshank breeding season also negatively impacted nest survival but to a lesser extent. Identifying the key environmental variables that influence Redshank nest survival should assist conservation managers to reflect on strategies to maintain this vulnerable species whilst also conserving other target species. Overall, this project highlights, (i) the benefits of retesting established survey methods and developing improved population estimates, (ii) the need to address the impact of both wildfowl and livestock grazing in future research and conservation management for Redshank, and (iii) the value of long- term data that permit new insights into population dynamics of species

    The role of waterbirds in the dispersal of aquatic organisms in southern Africa

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    Dispersal is a fundamental process with far-reaching ecological and evolutionary consequences. Not all organisms are capable of dispersing on their own and instead produce propagules that must be transported to new habitat by a vector. Propagule dispersal by frugivorous bird species is well researched, but only very recently has the capacity of highly mobile waterbirds to disperse aquatic organisms received similar attention in the dispersal literature. Dispersal is important for the organisation of communities, and therefore understanding the frequency and scale of waterbird-mediated dispersal provides insight into the structure of wetland communities. Additionally, the study of waterbird-mediated dispersal in arid southern Africa provides an opportunity to expand our knowledge on the persistence of populations of aquatic organisms in heterogeneous environments. Recently, field and laboratory studies have demonstrated the remarkable ability of waterbirds to disperse the propagules of both plants and aquatic invertebrates. However, these studies have largely been based in the northern hemisphere and many have focussed on long-distance dispersal by migratory waterbirds. Therefore, it is difficult to generalise how waterbird-mediated dispersal plays out in different landscapes and throughout the annual cycle. Furthermore, there is still little knowledge of the spatial patterns of propagule dispersal and the mechanisms that cause these patterns to vary in space and over time. This thesis aims to addresses several of these knowledge gaps in waterbird-mediated dispersal and presents the first detailed study of propagule dispersal by waterbirds anywhere in Africa. In Chapters 2 - 5, I adopt a field- and experimental-based approach to develop a general understanding of waterbird-mediated dispersal in southern Africa. Firstly, making use of faecal samples and feather brushings collected from several waterfowl (duck) species at three locations in South Africa, I determine the quantity and viability of propagules transported via endozoochory and ectozoochory. I then assess the relative contributions of each dispersal mode to the dispersal of plants and aquatic invertebrates in the field. I show that endozoochory is the dominant dispersal mechanism, but it may be complementary to ectozoochory as different propagules are transported via this mode. Secondly, by making use of an experimental feeding trial with two captive waterfowl species, Egyptian Goose and Red-billed Teal, I explore how seed traits mediate a trade-off in recoverability and germinability against gut retention times. I show that small, hard-seeded species are retained for longer and therefore may be dispersed further. Thirdly, I incorporate gut retention time data and Egyptian Goose and Red-billed Teal movement data, acquired from GPS satellite transmitters across five study populations in southern Africa, into a mechanistic model to explore spatial patterns of seed dispersal. The model demonstrates that waterfowl generally facilitate dispersal on the local scale of below 5 km, but on occasion can transport seeds as far as 500 km from a seed source. There was variation in dispersal distances between the vectors and across the study populations and the results indicate that dispersal is affected by both intrinsic and extrinsic drivers of animal movement. In Chapters 6 and 7, I apply the concept of waterbird-mediated dispersal more broadly to address (1) the role of waterbirds in the dispersal of aquatic invaders; and (2) the determination of seed dispersal functional groups amongst a waterfowl community. I conducted a literature review to objectively describe the role of waterbirds in the dispersal of aquatic weeds. Waterbirds are important vectors of aquatic invasive species and consideration of the spatially explicit manner in which birds move is imperative to our understanding of invasive spread. In the second case, I used diet data from the 16 waterfowl species indigenous to southern Africa to explore whether finer level seed dispersal functional groups were evident. I found support for several functional groups of seed disperser based on unique plant families in the diet and suggest that important functional differences do occur between groups of waterfowl species

    How will climate change affect endangered Mediterranean waterbirds?

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    Global warming and direct anthropogenic impacts, such as water extraction, largely affect water budgets in Mediterranean wetlands, thereby increasing wetland salinities and isolation, and decreasing water depths and hydroperiods (duration of the inundation period). These wetland features are key elements structuring waterbird communities. However, the ultimate and net consequences of these dynamic conditions on waterbird assemblages are largely unknown. We combined regular sampling of waterbird presence through one annual cycle with in-situ data on relevant environmental predictors of waterbird distribution to model habitat selection for 69 species in a typical Mediterranean wetland network in southwestern Spain. Species associations with environmental features were subsequently used to predict changes in habitat suitability for each species under three climate change scenarios (encompassing changes in environmental predictors that ranged from 10% to 50% change as predicted by regional climatic models). Waterbirds distributed themselves unevenly throughout environmental gradients and water salinity was the most important gradient structuring the distribution of the community. Environmental suitability for the guilds of diving birds and vegetation gleaners will decline in future climate scenarios, while many small wading birds will benefit from changing conditions. Resident species and those that breed in this wetland network will also be more negatively impacted than those using this area for wintering or stopover. We provide a tool that can be used in a horizon-scanning framework to identify emerging issues in waterbird conservation and to anticipate suitable management actions
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