. 2013. Avian mortalities due to transmission line collisions: a review of current estimates and field methods with an emphasis on applications to the Canadian electric network. Avian Conservation and Ecology 8(2): 7. http://dx.doi.org/10.5751/ACE-00614-080207 ABSTRACT. Birds are vulnerable to collisions with human-made fixed structures. Despite ongoing development and increases in infrastructure, we have few estimates of the magnitude of collision mortality. We reviewed the existing literature on avian mortality associated with transmission lines and derived an initial estimate for Canada. Estimating mortality from collisions with power lines is challenging due to the lack of studies, especially from sites within Canada, and due to uncertainty about the magnitude of detection biases. Detection of bird collisions with transmission lines varies due to habitat type, species size, and scavenging rates. In addition, birds can be crippled by the impact and subsequently die, although crippling rates are poorly known and rarely incorporated into estimates. We used existing data to derive a range of estimates of avian mortality associated with collisions with transmission lines in Canada by incorporating detection, scavenging, and crippling biases. There are 231,966 km of transmission lines across Canada, mostly in the boreal forest. Mortality estimates ranged from 1 million to 229.5 million birds per year, depending on the bias corrections applied. We consider our most realistic estimate, taking into account variation in risk across Canada, to range from 2.5 million to 25.6 million birds killed per year. Data from multiple studies across Canada and the northern U.S. indicate that the most vulnerable bird groups are (1) waterfowl, (2) grebes, (3) shorebirds, and (4) cranes, which is consistent with other studies. Populations of several groups that are vulnerable to collisions are increasing across Canada (e.g., waterfowl, raptors), which suggests that collision mortality, at current levels, is not limiting population growth. However, there may be impacts on other declining species, such as shorebirds and some species at risk, including Alberta's Trumpeter Swans (Cygnus buccinator) and western Canada's endangered Whooping Cranes (Grus americana). Collisions may be more common during migration, which underscores the need to understand impacts across the annual cycle. We emphasize that these estimates are preliminary, especially considering the absence of Canadian studies.RÉSUMÉ. Les oiseaux sont vulnérables aux collisions avec les structures fixes d'origine anthropique. Malgré le développement continuel et l'augmentation du nombre d'infrastructures, nous avons peu d'estimations sur l'ampleur de la mortalité par collision. Nous avons procédé à une revue de la littérature touchant la mortalité aviaire associée aux lignes de transport d'électricité et avons calculé une estimation préliminaire pour le Canada. L'estimation de la mortalité attribuable aux collisions avec les lignes électriques pose un défi en raison du manque d...
Aim High-latitude ectotherms are predicted to be less physiologically vulnerable to climate warming than tropical species based on their larger thermal safety margins, the distance between ambient temperatures and species' thermal optima. We sought to test the prediction that high latitude amphibians are buffered against the impacts of climate warming.Location British Columbia, Canada.Methods We estimated the risk from climate change for three high-latitude amphibian species (Spea intermontana, Rana aurora and Pseudacris regilla) by combining thermal performance experiments with species distribution models and predicted changes in maximum summer temperatures through the 2080s, in order to demonstrate temporal and geographical trends in vulnerability to climate warming among and within species. ResultsWe found that species have thermal safety margins of 3.2-3.8°C based on current maximum summer temperatures. However, by the 2080s (emissions scenario A1B), we estimate that 45-82% of our focal species' current distributions will experience maximum summer temperatures above their thermal optima. We also found that by using long-term average temperatures, as some studies have done, there were almost no scenarios in which populations of any species were experiencing temperatures greater than their thermal optima.Main conclusions Combining spatially explicit species distribution models with performance physiology allows us to predict where limiting temperatures will occur in the coming decades, and can guide climate mitigation and conservation efforts before populations decline. Despite moderate thermal safety margins, high-latitude ectotherms can be highly vulnerable to climate warming when spatio-temporal variation is incorporated into estimates of risk as a result of climate change.Embryos were reared under common outdoor conditions, and larvae were housed separately by species in plastic wading pools containing pond water and leaf litter from their
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