Resource Documents: Raptors (5 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”
Action on multiple fronts, illegal poisoning and wind farm planning, is required to reverse the decline of the Egyptian vulture in southern Spain
Author: Sanz-Aguilar, Ana; et al.
Large body-sized avian scavengers, including the Egyptian vulture (Neophron percnopterus), are globally threatened due to human-related mortality so guidelines quantifying the efficacy of different management approaches are urgently needed. We used 14 years of territory and individual-based data on a small and geographically isolated Spanish population to estimate survival, recruitment and breeding success. We then forecasted their population viability under current vital rates and under management scenarios that mitigated the main sources of non-natural mortality at breeding grounds (fatalities from wind farms and illegal poisoning). Mean breeding success was 0.68 (SD = 0.17) under current conditions. Annual probabilities of survival were 0.72 (SE = 0.06) for fledglings and 2 yr old non-breeders, 0.73 (SE = 0.04) for non-breeders older than 2 yrs old and 0.93 (SE = 0.04) for breeders. Probabilities of recruitment were 0 for birds aged 1–4, 0.10 (SE = 0.06) for birds aged 5 and 0.19 (SE = 0.09) for older birds. Population viability analyses estimated an annual decline of 3–4% of the breeding population under current conditions. Our results indicate that only by combining different management actions in the breeding area, especially by removing the most important causes of human-related mortality (poisoning and collisions on wind farms), will the population grow and persist in the long term. Reinforcement with captive breeding may also have positive effects but only in combination with the reduction in causes of non-natural mortality. These results, although obtained for a focal species, may be applicable to other endangered populations of long-lived avian scavengers inhabiting southern Europe.
Ana Sanz-Aguilar, José Antonio Sánchez-Zapata, Martina Carrete, José Ramón Benítez, Enrique Ávila, Rafael Arenas, José Antonio Donázar
Dept of Conservation Biology, Estación Biológica de Doñana (CSIC), Sevilla; Population Ecology Group, Instituto Mediterráneo de Estudios Avanzados (CSIC-UIB), Islas Baleares; Área de Ecología, University Miguel Hernández, Alicante; Universidad Pablo de Olavide, Sevilla; Línea de Geodiversidad y Biodiversidad, Agencia de Medioambiente y Agua, Junta de Andalucía, Sevilla; and Gestión del Medio Natural, Dirección Provincial de Córdoba, Consejería de Medio Ambiente, Junta de Andalucía, Córdoba, Spain
Biological Conservation 187 (2015) 10–18. doi: 10.1016/j.biocon.2015.03.029
Author: Watson, Richard; et al.
ABSTRACT.—The global potential for wind power generation is vast, and the number of installations is increasing rapidly. We review case studies from around the world of the effects on raptors of wind-energy development. Collision mortality, displacement, and habitat loss have the potential to cause population-level effects, especially for species that are rare or endangered. The impact on raptors has much to do with their behavior, so careful siting of wind-energy developments to avoid areas suited to raptor breeding, foraging, or migration would reduce these effects. At established wind farms that already conflict with raptors, reduction of fatalities may be feasible by curtailment of turbines as raptors approach, and offset through mitigation of other human causes of mortality such as electrocution and poisoning, provided the relative effects can be quantified. Measurement of raptor mortality at wind farms is the subject of intense effort and study, especially where mitigation is required by law, with novel statistical approaches recently made available to improve the notoriously difficult-to-estimate mortality rates of rare and hard-to-detect species. Global standards for wind farm placement, monitoring, and effects mitigation would be a valuable contribution to raptor conservation worldwide.
RICHARD T. WATSON
The Peregrine Fund, Boise, Idaho, USA
PATRICK S. KOLAR
Raptor Research Center, Department of Biological Science, Boise State University, Idaho, USA
Delegación del CSIC en Andalucía—Casa de la Ciencia, Sevilla, Spain
Norwegian Institute for Nature Research, Trondheim
Ecosystem Science and Management, University of Northern British Columbia, Prince George, Canada
W. GRAINGER HUNT
The Peregrine Fund, Boise, Idaho, USA
HANNELINE A. SMIT-ROBINSON
BirdLife South Africa, Parklands, South Africa; and Applied Behavioural Ecological & Ecosystem Research Unit, UNISA, Florida, South Africa
CHRISTOPHER J. FARMER
DNV GL—Energy, Chalfont, Pennsylvania, USA
US Geological Survey Forest and Rangeland Ecosystem Science Center, Corvallis, Oregon, USA
TODD E. KATZNER
US Geological Survey Forest and Rangeland Ecosystem Science Center, Boise, Idaho, USA
The Journal of Raptor Research, March 2018, Vol. 52, No. 1
Download original document: “Raptor Interactions with Wind Energy: Case Studies from Around the World”