Have you ever questioned why wild birds sitting way up high on electricity pylons do not get electrocuted? Suppose you were a child of the 70s and lived in the UK. In that case, you may remember having to sit through many educational videos at school that explained the dangers associated with electrical pylons so why is it that birds can sit on overhead powerlines without being shocked or killed?
Birds do not get electrocuted while sitting on electricity pylon cable because both the bird’s feet are on the same potential, so electricity does not flow through the bird. The bird also offers greater resistance than the power cable, so the electricity continues to flow through the power cable. However, if the bird were to touch another cable, the ground of something else, the electricity will travel through the bird and into this ground, shocking or killing it.
If this sounds confusing, then continue reading, and I will explain a little more about electricity and why we do not see hundreds of wild birds laying dead around the base of these electrical pylons.
The first thing we need to understand is that the electrical current is a movement of electrons that travel from power stations, into our homes, around all the plugs and eventually making its way back to the power station. You may have head electricians refer to this as a closed-loop. This closed-loop is required to make the electrons flow.
You may have heard the expression that electricity is very lazy, a term that helps explain how electricity will react with its surroundings. Imagine for a moment that you are standing at the top of a hill and you release several large round boulders at the top.
You know that they will go downhill (assuming they are not blocked!) and will continue on any path available. Electrons move from the higher potential to the lower potential in much the same way.
When a bird sits on an electrical pylon wire, both of its feet are actually on the same electrical potential, and so no electrons move through the bird’s body. The critical point here is that the bird does not touch anything else; it remains on one wire.
If the bird were to touch another wire, especially one with a different potential, electricity would try and pass through the bird, ultimately resulting in the bird being shocked or killed.
You may have noticed that the large electrical cables on these pylons are often held apart so that they do not sway in the wind and touch, but on poorly maintained cables around cities, this is not always the case.
Greater risk for the bird comes when it decides to perch on top of an electricity pylon wooden pole as these poles are buried in the ground (grounded) and therefore have a very low electrical potential.
If a bird sits on the wooden pole that is grounded and then touches a live wire, the electrical current will immediately pass through the birds’ body and head straight for the lowest potential, which would be the telegraph pole.
Although the distance between many of the power lines on an electrical pylon is quite large, there are a surprising number of fatalities of wild birds each year.
An even more distressing fact is that many of these electrocution events are by birds with larger wingspans such as eagles and osprey which are also known to take a liking to build their nests on these high up poles. Unfortunately, many of these birds are on the endangered list so it’s always upsetting to learn of it happening.
This is also why it is so dangerous for humans to touch live wires. In the vast majority of cases, we will always be standing on the floor and so always grounded.
Any current will try and pass through us and into the ground. Rubber-soled shoes can protect you from this, but these shoes must be 100% rubber (not just a pair of running shoes you think have some rubber!). Rubber is an insulator, a material in which an electrical charge can’t flow through you to get to the ground.
A fantastic video demonstrating this effect can be found below:
Why do birds like to perch on powerlines?
Wild birds legs and feet are specially adapted to holding onto trees and branches. Birds use their legs in various ways from perching, walking, scratching and in birds of prey – for weapons. While humans’ feet vary little from one person to the next, wild birds’ feet can vary considerably and can be quite specialised depending on the need.
The majority of UK garden birds have three toes facing forward and one facing the back, but some are slightly different. Swifts can often be seen resting vertically on walls and have all their toes facing the same direction (pamprodactyl). Gamebirds and chickens typically have a fifth toe with a sharp claw used to fight or defend itself.
Woodpeckers and parrots are known to have two facing forward and two facing backwards (zygodactyl). In the woodpecker case, it allows it to hang vertically from a tree trunk and in the case of the parrot, enable it to walk up and down tree trunks with ease.
Wild birds’ feet are usually made up of tendons and bones, covered with hard scaled skin. Their feet do contain very few nerves or blood vessels so they can land on cold metal perches even though temperatures may be freezing.
The reason that birds sit on powerlines is nothing more than an ideal perch, up high and away from predators. Wild birds are particularly well suited to perching as the tendon that flexes their toe runs along the outside of their ankle and knee. As a result, when the bird’s joints bend, the toes clench automatically, gripping tightly to the perch even when the bodies are at rest. This is perfect for the bird’s rest or sleep periods when there is a need to recuperate while staying out of predators’ reach.
While we are talking about wild birds feet, you may have also questioned why their knees appear to bend backwards!
Why do birds knees bend backwards?
Although a bird’s knees appear to bend backwards, they don’t. When we look at a bird, we are not seeing their knees but seeing their ankles instead. A bird’s knees are actually much further up its body, often concealed beneath its feathers. Directly below their knees is their foot which if you think about it, means that the birds are actually standing on tiptoes.
Why do birds on a wire all sit in the same direction?
While wild birds sitting on overhead wires may face the same direction, it is unlikely that all birds will do this. One possible reason why birds face the same direction could be to do with the wind direction. Humans and birds alike have learned that it is easier to take off into the direction of the wind than with it. Another reason could be that the birds simply want to avoid the wind blowing in the opposite direction to their feathers.
Why don’t squirrels get electrocuted on power lines?
Squirrels are at risk of electrocution in precisely the same way as wild birds. If the squirrel comes into contact with two different wires, there is a risk of shock or death.
Why do bats get electrocuted on power lines?
For the same reason, that larger birds of prey get electrocuted on power lines. Bats wingspans are known to be quite large in comparison to their bodies. While a bat remains on a single electrical pylon wire, it is safe, but if its wings outstretched were to touch another wire, it is at risk of shock or death.