Bird Flappers for Overhead Power Line Collision Mitigation

August 22, 2019

Bird Flappers or Diverters
Bird Flappers by Balmoral

Bird Flappers or Diverters as they are commonly known in the industry, have proven to be an essential tool in the ongoing effort to help protect birds from colliding with power lines. As the solutions and types of flappers or diverters on the market become more finely tuned, in theory, this should result in a reduction in the number of bird collisions into overhead power lines where these have been deployed.

There are two basic types or styles of bird flappers.

  1. Fixed – these are the traditional design, typically shaped like a spiral or coil and are wrapped around the conductor or power line typically by hand. Their main benefit is their durability due to lack of moving parts. The downside of this, however, is that they are less conspicuous to the bird and hence may not be as effective at mitigating power line collisions.
  2. Dynamic – these devices, known typically as flappers, have a clamping mechanism which affixes to the power line and a lower section which dangles beneath providing the visual warning aspect to deter birds. Being a dynamic device, the engineering and durability of design are all important as these devices can be more vulnerable to wear and tear over the longer term. The benefit of including an element of movement in the device is that it will compete for the bird’s attention even when not in the direct line of sight of the bird.

Ultimately, when a Power Transmission or Distribution company seeks to install such devices to reduce or eliminate the impact of bird wire strikes on their network, the durability of the devices becomes a critical factor. Often lower cost devices may appear attractive from the outset when a complete understanding of the whole of life costs are unknown or uncertain.

Utility companies are always proactively seeking ways to improve the reliability of their networks to ensure reliable power supply to their customers. The impact of wildlife on the power grid, while understood by Utility Engineers, is often somewhat difficult to quantify. What is understood, is that birds colliding with Power Lines has a dramatic impact on bird survival rates as well as compromising the integrity of the power grid with possible asset damage or failure.

Environmental issues are becoming more prominent than ever before. As population centers throughout the world continue to expand, the infrastructure to support this expansion must keep up. This situation is even more acute in developing countries where at times, the electrical infrastructure can be historically underdeveloped. When governments and private investment then begin to focus on this issue, we can see a rapid rate of expansion. This can typically challenge natural environments and their inhabitants.

There is much scientific and anecdotal evidence to show that bird flappers and diverters provide an effective mitigation measure against bird collisions with power lines. The problem of birds colliding with power lines is not restricted to certain species, with a cross-section of different birds vulnerable, but for different reasons.

Migratory birds can often fall victim to power line collisions, especially when such power lines cross their natural migration pathways. This anecdotally seems even more pronounced near waterways or coastlines. Both transmission and distribution lines can have an impact here. Transmission lines tend to be higher in the air, and their earth or ground wire can be very difficult to detect. There is a known phenomenon, whereby bird(s) may see the larger and more visible transmission phase wires, adjust course by moving upwards which takes them directly into the thinner and harder to see earth/ground wire.

It is for this reason that it is the earth or ground wire, which is commonly marked by bird diverters. Because the earth or ground wire remains inactive electrically, the complications of extra-high voltage and ozone or corona generation are not relevant.

Bird Flappers or Diverters

Even birds with excellent acuity of vision such as eagles and raptors can fall victim to power line collisions. This is due to behavioral issues as opposed to poor eyesight. Raptors may display foraging behavior whereby they focus their attention on the ground while maintaining their flight path. This renders them effectively blind in a horizontal trajectory from their flight path. In an evolutionary sense, this is not problematic, because their altitudes are well above the tree lines and hence they are unlikely to fly into any obstructions as this height. Unfortunately, distribution and transmission wires provide a relatively hard to see obstacle which can impact on the raptors flight path.

In the above situation, the benefits of dynamic diverter devices become more pronounced.  The element of movement competes for the attention of the bird, therefore, even if the bird is focused elsewhere (e.g., the ground for prey), a flapping bird diverter may be sufficient to catch its attention for long enough for the bird to recognize a potential obstacle and maneuver around it. Other important elements in the bird flapper design include contrasting colors. This renders the device visible, independent of background lighting conditions.

This is known as internal contrast and can help in a range of lighting conditions. Elements on the device, which are black and white, provide the highest possible internal contrast. The size of the device is also important given the relative low acuity of some birds, enabling these particular species to see from farther away. The farther away these devices can be seen, the greatest chance for the bird to effect an evasive maneuver in time to miss the power line.

In summary, there is a range of bird flappers on the market today with a range of different feature sets. It is important to consider all these factors and the target species of birds when making selection decisions.

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