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©Ricardo Martins_Cranes

Reducing Bird Collision

© Ricardo Martins


Bird mortality due to collision with power lines can happen on distribution or transmission electricity grids. The main reason for collision is a bird's inability to perceive the overhead wires has an obstruction in the airspace upon approach. Thus, and although bird collisions can occur both with conductors and earth wires, they are most often a problem with the thin ‘earth wire’ at the top of high-voltage power lines.

©Ricardo Martins_White stork

© Ricardo Martins


Along with infrastructure features (wire diameter, pylon configuration and height), environmental factors such as topography, habitats, weather and light conditions can also influence the potential for bird collisions with power lines.  For instance, power lines that cross the bird species' regular migration routes can be especially problematic and the risk of collision with those infrastructure is a major cause of mortality for some bird species.





  • Topography

  • Habitat features

  • Weather and light conditions

  • Anthropogenic disturbance

  • Sensory perception (vision, etc.)

  • Morphological features

  • Flight behaviour

  • Phenology

  • Circadian habits

  • Age, sex and health


  • No. of vertical wire levels

  • Pylon and wire height
  • Conductors and earth wire diameter

Adapted from Bernardino et al. (2021)

The susceptibility of birds to collision is also greatly determined by species characteristics, including their morphology, flight behavior, phenology, and age. For example, larger, heavier birds with short wing spans and poor vision – and thus lower manoeuvrability - such as White Storks and Little Bustards, have a greater risk to collide with power lines.

Moreover, species with a long lifespan, low breeding rate and/or which are rare or already vulnerable in terms of conservation status (such as Eagles, Vultures and Black Storks) are particularly at risk.

Little Bustard © Joerg Mager

© Joerg Mager

Bonelli's eagle © Vincent Palomares

© Vincent Palomarès


Placing power lines underground has been identified as the most effective solution to prevent risk of collision and electrocution for bird’s population. However, this is not always possible due to potentially greatly higher costs, or technical factors. Thus, when dangerous power lines cannot be put underground, marking the lines with ‘Bird Flight Diverters’ is one of the best mitigation solutions chosen worldwide.

A vast range of wire-marking devices has been developed over the years, including:



Double-ended spiral devices with large dimensions (ca. 1 m long) but static and only visible to birds during daylight



Dynamic devices in the shape of e.g. plates that rotate in the wind. Some devices have reflective and luminescent parts to make them visible in daylight as well as at night to birds



25-cm spheres with one side in red and one side that lights up at night

It is important to note, that the effectiveness of these markers is still contested and varies according to species, geography, and other factors (e.g. distance between markers).

© RPS Avian sphere on high voltage line


In the SafeLines4Birds project, innovative approaches will therefore be adopted including the test of new Bird Flight Diverters, such as the American ultra-violet Avian Collision System Avoidance System, novel installation methods of wire-markers, and new monitoring methods of bird collisions based on visual/thermal cameras.
Moreover, the project also aims to install 3,880 existing anti-collision devices on the most dangerous sites and assess the effectiveness of those wire-markers in reducing bird collision rates.
In some cases, lines will also be placed underground to completely eliminate the risk of collision and electrocution in particularly high-risk areas.


Electrocution is a problem mainly linked to the medium voltage type of power lines, where perching individuals can be electrocuted due to a short distance between the conductors or between the conductors and the power pole.

Mortality caused by electrocution can have a significant impact on the survival of certain bird species and result in the loss of many thousands of individuals each year (McClure et al., 2018; Guil et al., 2022).

RTE Travaux Préguillac - Cigogne et pylône


© RPS Buzzards victims of electrocution


Risk of electrocution is attributed to different variables:

  • Species-specific characteristics, size and behaviour

  • Surroundings conditions such as the proximity of power lines in relation to the birds’ activities. For example, some species as White Storks uses power tower as nesting sites

  • Combination of two features specific to power lines: the design and the materials used


There is a strong scientific consensus that the electrocution risk for birds depends on the technical construction and design of the power poles and towers.

The best solutions to prevent electrocution are those which allow the birds to perch safely on electric poles. Replacing dangerous, poorly designed poles can also drastically reduce bird casualties caused by electrocution.

The SafeLines4Birds project aims to neutralise dangerous poles and install bird deterrence devices on the sites with the highest risk. Platforms and perches to reduce the risk when birds roost or nest will also be installed. The safest pylons designs will also be catalogued, tested, and installed as part of the project, in order to eliminate the risk at source.

© RPS Bird perching


© RPS Installation BFD


Large birds of prey, such as Bearded vultures or Osprey but also other species such as Storks, are particularly sensitive to disturbance during their breeding season. This can lead to the temporary or permanent abandonment of the nest, leaving it open to predators, or to unsuccessful breeding.


Therefore, the lack of population growth may eventually lead to the disappearance of those species in the area. This impact will be even more dramatic if the population size is already low.

Disturbance concerns all maintenance or monitoring operations on power lines and networks likely to impact breeding of certain species. Whether caused by maintenance workers attending to the pylons, or by helicopter flying overhead (e.g. for maintenance, to fit Bird Flight Diverters), all of these activities have the potential to create disturbance.

White stork E-REDES



SafeLines4Birds aims to reduce disturbance and nest abandonment during breeding season by adapting, where possible, grid maintenance and surveillance in line with the breeding periods of the target species, and thus improve their breeding success. Flying over breeding sites will be avoided as much as possible, and where possible helicopters will be limited. Operators will be trained to monitor the species more closely.


Given the limitations of carcass research and mortality data in these large areas, the impact of the lines is largely underestimated and therefore, in addition to the difficulty to identify responsible lines, insufficiently resolved.

The lack of data and knowledge due to difficulties in monitoring bird electrocutions and collisions (e.g. non-standardisation in data collection, difficulties on carcass recovering or determining the exact cause of death) is a major obstacle to accurately estimate the effect of power lines on birds and the effectiveness of mitigation measures.

© James Dwyer_Visit ACAS BE

© James Dwyer


The project will provide a wealth of data and knowledge on the interactions between birds and power lines. In addition to carcass searches, visual and thermal cameras will be used to monitor bird collision with power lines, improving the accuracy of mortality estimates, and to study bird behaviour around the lines.


Furthermore, we will gather data and experiences of all European grid operators and associations in a European platform. All the data collected will be handled in an open and transparent way, made available on the SafeLines4Birds open digital platform. This will facilitate the dissemination of knowledge regarding technical innovations and equipment across Europe and, through this, support the replication of actions in other countries.

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