Voltage is not the whole story
A wire can be at a very high voltage and still not send a dangerous current through a bird perched on it.
For current to move through the bird's body, there needs to be a meaningful voltage difference from one part of the bird to another and a path for current to follow.
Put both feet on essentially the same point electrically, and that difference is tiny.
What does “same electrical potential” mean?
Think of electrical potential a little like height.
Water flows downhill because there is a difference in height. Electrical current flows when there is a difference in electrical potential and a conductive path connecting the two points.
A small bird's feet may be several centimetres apart on the same conductor, but the voltage difference between those two nearby points is generally very small. Not zero in a perfect physics sense. Small enough that dangerous current does not normally pass through the bird.
Why would a person be in danger?
Because a person touching an energized conductor while also connected to the ground can create a very different path.
The voltage difference between the conductor and ground can be huge. Current can then pass through the body.
This is also why you should never treat the bird example as a lesson in how a person could safely touch a power line. It is not.
Can a bird get electrocuted if it touches two wires?
Yes.
If the two wires are at different electrical potentials and the bird bridges them, current can flow through its body from one to the other. The same danger exists if the bird touches an energized conductor and a grounded metal part at the same time.
That is one reason larger birds face more risk around some distribution equipment. An eagle or hawk can reach farther than a sparrow.
Why are power poles dangerous to eagles and hawks?
Large raptors like high perches. Power poles can give them an excellent view of open country.
The problem comes when electrical components are close enough for a large bird to bridge them. Audubon and the U.S. Geological Survey both describe electrocution when birds contact two energized parts, or an energized part and grounded equipment.
Utilities can reduce that risk with better spacing, insulation, perch design, and other bird-safe construction practices.
Are feathers what keep birds safe?
Not really.
Dry feathers are not great conductors, but the main protection for a bird sitting on one wire is electrical geometry, not a magic insulating coat.
If the bird bridges a dangerous voltage difference with its feet, beak, skin, or other conductive contact, feathers may not save it. Wet conditions can make things worse.
Why doesn't electricity just jump into the bird?
Electricity is already moving through a very good conductor: the wire.
There is no strong reason for a large current to detour through a bird whose feet are at nearly the same potential. Current follows the complete electrical conditions of the circuit, not simply whatever living thing happens to touch the wire.
That is the part that feels counterintuitive. Touching voltage is not the same thing as having dangerous current driven through your body.
Can electricity arc to a bird?
It can under the right conditions.
Very high voltages can arc through air across a gap, and electrical equipment can produce dangerous faults. Birds do not have to be neatly gripping two bare wires with their feet for electrocution to happen.
Again, size and equipment design matter.
What about birds sitting shoulder to shoulder?
A line of small birds can sit on one conductor without creating the same kind of path to ground or another electrical phase.
They are touching one another, but they are still all sitting at nearly the same potential if they remain on the same conductor and away from other conductive parts.
It looks risky. Electrically, the setup can be quite ordinary.
Are all power lines equally dangerous to birds?
No.
Transmission lines, distribution lines, transformers, crossarms, insulators, and pole hardware are built in different ways. The spacing between energized components varies. So does voltage.
Audubon's transmission work notes that electrocution risk is generally lower on high-voltage transmission structures where conductors are spaced much farther apart, while distribution poles can create hazards for large perching birds if energized parts are close together.
Birds can also collide with wires
Electrocution is only one power-line problem.
Cranes, waterfowl, grouse, and other birds can collide with wires, particularly when visibility is poor or the line is difficult to see. Utilities and conservation groups use markers and other approaches to make risky spans more visible.
So a wire may be electrically safe for a perched sparrow while still being a collision hazard for another bird in flight.
Frequently asked questions
Why can a bird sit on a 10,000-volt wire?
Because voltage relative to ground is not enough by itself. With both feet on the same conductor, there is little voltage difference across the bird's body and therefore little current through it.
Would a bird be electrocuted if one foot touched the ground?
If a bird somehow maintained contact with an energized conductor and ground at the same time, that could create a dangerous path. In real utility settings, the geometry is more complicated, but the principle is the same.
Why don't squirrels get electrocuted?
The same electrical principle can protect other animals when they touch only one conductor and do not bridge to another potential. Squirrels can still be electrocuted when they contact multiple parts of electrical equipment.
Can rain make power lines more dangerous for birds?
Wet feathers and wet equipment can increase conductivity and change risk. The exact danger depends on the equipment and how the bird makes contact.
It comes down to the circuit
The simple version is this: one wire, nearly the same potential under both feet, very little current through the bird.
Bridge two different potentials and everything changes.
Continue with why birds sit on power lines, whether birds can fly backwards, or return to Bird Facts.