Resource Documents: Birds (44 items)
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Author: Law, Peter; and Fuller, Mark
Anthropogenic alterations to landscape are indicators of potential compromise of that landscape’s ecology. We describe how alterations can be assessed as ‘hazards’ to wildlife through a sequence of three steps: diagnosing the means by which the hazard acts on individual organisms at risk; estimating the fitness cost of the hazard to those individuals and the rate at which that cost occurs; and translating that cost rate into a demographic cost by identifying the relevant demographically-closed population. We exploit the conservation-oriented literature on wind farms to illustrate this conceptual scheme. For wind farms, the third component has received less attention than the first two, which suggests it is the most challenging of the three components. A wind farm provides an example of a ‘spatially localized hazard’, i.e., a discrete alteration of landscape hazardous to some population but of which there are some individuals that do not interact directly with the hazard themselves but nevertheless suffer a reduction in fitness in terms of their contribution to the next generation. Spatially localized hazards are identified via the third component of the scheme and are of particular conservation concern as, by their nature, their depredations on wildlife may be underestimated without an appropriate population-level estimation of the demographic cost of the hazard.
Peter R. Law, Centre for African Conservation Ecology, Department of Zoology, Nelson Mandela University, South Africa
Mark Fuller, Forest and Rangeland Ecosystem Science Center, U.S. Geological Survey, Boise, Idaho
Ecological Indicators 94 (2018) 380–385
Download original document: “Evaluating anthropogenic landscape alterations as wildlife hazards, with wind farms as an example”
Author: Hunt, W. Grainger; et al.
Raptors are exposed to a wide variety of human-related mortality agents, and yet population-level effects are rarely quantified. Doing so requires modeling vital rates in the context of species life-history, behavior, and population dynamics theory. In this paper, we explore the details of such an analysis by focusing on the demography of a resident, tree-nesting population of golden eagles (Aquila chrysaetos) in the vicinity of an extensive (142 km²) windfarm in California. During 1994–2000, we tracked the fates of >250 radio-marked individuals of four life-stages and conducted five annual surveys of territory occupancy and reproduction. Collisions with wind turbines accounted for 41% of 88 uncensored fatalities, most of which were subadults and nonbreeding adults (floaters). A consistent overall male preponderance in the population meant that females were the limiting sex in this territorial, monogamous species. Estimates of potential population growth rate and associated variance indicated a stable breeding population, but one for which any further decrease in vital rates would require immigrant floaters to fill territory vacancies. Occupancy surveys 5 and 13 years later (2005 and 2013) showed that the nesting population remained intact, and no upward trend was apparent in the proportion of subadult eagles as pair members, a condition that would have suggested a deficit of adult replacements. However, the number of golden eagle pairs required to support windfarm mortality was large. We estimated that the entire annual reproductive output of 216–255 breeding pairs would have been necessary to support published estimates of 55–65 turbine blade-strike fatalities per year. Although the vital rates forming the basis for these calculations may have changed since the data were collected, our approach should be useful for gaining a clearer understanding of how anthropogenic mortality affects the health of raptor populations, particularly those species with delayed maturity and naturally low reproductive rates.
W. Grainger Hunt, J. David Wiens, Peter R. Law, Mark R. Fuller, Teresa L. Hunt, Daniel E. Driscoll, Ronald E. Jackman
The Peregrine Fund, Boise, Idaho; Predatory Bird Research Group, Long Marine Laboratory, University of California, Santa Cruz; Forest and Rangeland Ecosystem Science Center, United States Geological Survey, Corvallis, Oregon; Centre for African Conservation Ecology, Nelson Mandela Metropolitan University, Port Elizabeth, Republic of South Africa; Forest and Rangeland Ecosystem Science Center, United States Geological Survey, Boise, Idaho; Garcia and Associates, San Anselmo, California; American Eagle Research Institute, Apache Junction, Arizona
PLoS ONE 2017;12(2):e0172232
Download original document: “Quantifying the demographic cost of human-related mortality to a raptor population”
Wind farms affect the occurrence, abundance and population trends of small passerine birds: The case of the Dupont’s lark
Author: Gómez-Catasús, Julia; Garza, Vicente; and Traba, Juan
1. The assessment of the effects of wind farms on bird populations is commonly based on collision fatality records. This could undervalue the effect of wind farms on small-sized birds. We evaluate the effect of wind turbines on occurrence, abundance and population trends of a threatened small passerine species, the Dupont’s lark Chersophilus duponti. To our knowledge, this is one of the first studies addressing the effect of wind farms on population trends using time-series data from multiple wind farms.
2. We estimated population trends by fitting a switching linear trend model with the software TRIM (Trend & Indices for Monitoring data). We used multiannual data surveys of five populations in the presence of wind farms and nine in their absence (2008–2016 period). Furthermore, we fitted a logistic and a negative binomial regression model to test the effect of wind farm proximity on species occurrence and abundance in 2016, respectively. We incorporated local connectivity and habitat availability estimates in both models as predictors.
3. Results showed a negative trend overall, but that was significantly more regressive in the presence of wind farms: 21.0% vs. 5.8% average annual decline in the absence of wind farms.
4. Dupont’s lark occurrence and abundance in 2016 were negatively affected by measures of population isolation and positively affected by the distance to wind farms.
5. These results highlight the negative effect of isolation and wind farm proximity on Dupont’s lark population parameters. Taking into account the metapopulation structure exhibited by the species in the study area, this work established a 4.5-km threshold distance from wind farms, beyond which Dupont’s lark populations should be unaffected.
6. Synthesis and applications. This work highlights the negative impact of wind farms on small-sized birds and provides a 4.5-km threshold distance that should be taken into account in the design of future wind energy projects. Moreover, we suggest an analytical approach based on population trends, species abundance and occurrence variation in relation to wind farms, useful for the assessment of wind farm impacts on small-sized birds.
Julia Gómez-Catasús, Vicente Garza, Juan Traba
Department of Ecology, Universidad Autónoma de Madrid, Spain
Journal of Applied Ecology 2018;1–10. DOI: 10.1111/1365-2664.13107
Effects of development of wind energy and associated changes in land use on bird densities in upland areas
Author: Fernández‐Bellon, Darío; et al.
Wind energy development is the most recent of many pressures on upland bird communities and their habitats. Studies of birds in relation to wind energy development have focused on effects of direct mortality, but the importance of indirect effects (e.g., displacement, habitat loss) on avian community diversity and stability is increasingly being recognized. We used a control‐impact study in combination with a gradient design to assess the effects of wind farms on upland bird densities and on bird species grouped by habitat association (forest and open‐habitat species). We conducted 506 point count surveys at 12 wind‐farm and 12 control sites in Ireland during 2 breeding seasons (2012 and 2013). Total bird densities were lower at wind farms than at control sites, and the greatest differences occurred close to turbines. Densities of forest species were significantly lower within 100 m of turbines than at greater distances, and this difference was mediated by habitat modifications associated with wind‐farm development. In particular, reductions in forest cover adjacent to turbines was linked to the observed decrease in densities of forest species. Open‐habitat species’ densities were lower at wind farms but were not related to distance from turbines and were negatively related to size of the wind farm. This suggests that, for these species, wind‐farm effects may occur at a landscape scale. Our findings indicate that the scale and intensity of the displacement effects of wind farms on upland birds depends on bird species’ habitat associations and that the observed effects are mediated by changes in land use associated with wind‐farm construction. This highlights the importance of construction effects and siting of turbines, tracks, and other infrastructure in understanding the impacts of wind farms on biodiversity.
Darío Fernández‐Bellon, Mark W. Wilson, Sandra Irwin, John O’Halloran
School of Biological, Earth and Environmental Sciences, University College Cork, Ireland
First published: 22 October 2018; https://doi.org/10.1111/cobi.13239
Download original document: “Effects of development of wind energy and associated changes in land use on bird densities in upland areas”
Download supplemental information: Details on site locations (Appendix S1), survey methods and density calculations (Appendix S2), and bird species recorded and their conservation status and densities (Appendix S3)