What we know (and don't know) about bird collisions with power lines and how to mitigate them
Written By Joana Bernardino
4th June 2021
Bird collisions with overhead wires are an significant source of mortality associated with both transmission and distribution power lines. This negative interaction raises, therefore, several conservation concerns as electricity grids are rapidly expanding worldwide, with up to approximately 8 trillion USD expected to be spent by 2040. We performed an extensive review of the existing literature on bird collisions with power lines to: (i) assess the known driving factors of bird collision; (ii) summarise and evaluate the existing mitigation measures; and (iii) identify knowledge gaps and opportunities for future research.
Our systematic literature search resulted in 208 studies focusing on bird collision with power lines, with the first ones being carried out in the early 1970s. More than 60% of the studies were focused on quantifying direct bird fatalities, but studies addressing collision risk factors (50%) and/or mitigation strategies (47%) were also relatively frequent. Studies that involved the collection of field data were conducted mainly in Europe and North America (43% and 35%, respectively), and transmission power lines were by far most studied (69%), compared to distribution lines (37%).
Understanding and mitigating bird collisions with power lines
The extensive scientific research conducted over the past decades has significantly increased our understanding of bird interactions with power lines. Avian collision risk with overhead wires is influenced by a wide range of factors which, for simplicity, we divided into three main groups: (1) species-specific factors (e.g., vision, morphology, phenology); (2) site-specific factors (e.g., topography, weather conditions, and habitat features); and (3) power line-specific factors (e.g., wire arrangement and diameter) (Fig. 1).
We evaluated the current knowledge on each of these factors by identifying the most consistently observed effects but also highlighting the different or even contradicting results achieved by the studies and the remaining knowledge gaps. Our review demonstrated that bird collision events are often explained by multiple collision risk factors, and often in unexpected or unpredictable ways, thereby limiting our ability to predict and mitigate bird collisions.
Figure 1. The three groups of factors that influence the rate of collision of birds with overhead power lines.
Over the years, several mitigation strategies have been adopted to decrease the risk of bird collision with power lines, although several still require further scientific evidence to demonstrate their effectiveness:
Underground cabling – Burying power lines is the only solution that completely prevents bird collisions but entails several technical and financial challenges.
Route planning – Strategic planning and careful routing to avoid, at a larger spatial scale, sensitive bird habitats, important migratory routes or protected areas; and, at a finer scale, sensitive nesting and foraging sites, main flight paths of resident species, etc. While expected to be very effective, this mitigation strategy has hardly been tested.
Power line configuration – Adoption, as much as possible, of configurations that e.g. reduce the number of vertical wire levels, kept the wires as low as possible, and increase cable thickness; although an insufficient number of studies have been conducted to demonstrate its effectiveness.
Wire-marking – Attaching flappers, spirals, or other markers to the overhead wires to increase their visibility for birds, is one of the most common and effective mitigation measures used worldwide.
Habitat management – The modification of habitats and the installation of visual stimuli (or sounds) near the power lines have been suggested to alert and/or help birds to change their local flight paths; but very few studies have tested the efficacy of such measures.
The need for more comprehensive and global research
Overall, our literature review shows that there is comparatively little scientific evidence on how the different power line-specific factors influence bird collision risk. More studies from Asia, Africa and South America are also needed, as addressing bird species or landscape features specific for these geographical regions will increase the overall knowledge on the topic. We also found that some existing recommendations of best practice to mitigate bird collisions still lack scientific evidence (e.g. clustering new power lines with other existing linear infrastructures; habitat management to reduce bird expose to power lines).
Based on these knowledge gaps, we outline suggestions for future research in three main areas: bird behaviour (e.g. further use of loggers and sensors), impact assessment (e.g. understanding the ecological drivers of mortality hotspots), and mitigation strategies (e.g. evaluate the effectiveness of different wire-marking devices and spacing between them).
Author information:
Joana Bernardino
Source:
Bernardino, J., Bevanger, K., Barrientos, R., J.F. Dwyer, J.F., A.T. Marques, A.T., Martins, R.C., Shaw, J.M., Silva, J.P. & Moreira, F. (2018). ‘Bird collisions with power lines: State of the art and priority areas for research’, Biological Conservation, 222: 1-13. doi: 10.1016/j.biocon.2018.02.029.
Editor:
Lucy Wairungi
Cite this summary:
Bernardino, J. 2021. What we know (and don’t know) about bird collisions with power lines and how to mitigate them. Edited by Wairungi, L. TransportEcology.info, Accessed at: https://transportecology.info/research/bird-collisions-with-powerlines [Date accessed].
