Birds are unharmed on high voltage lines, because they touch only one wire and don't experience voltage as the difference of potentials. However, birds also seem quite comfortable there. Could this be, because the wire is warmer than the air? The wire obviously has some resistance and the current generates some heat, so the wire is indeed warmer than the air. However, is it warmer enough for the birds to feel (say, by a degree)?

I hope someone with a knowledge of the typical magnitude of the current and wire cross section in high voltage lines (likely aluminum) would post an estimate of how much warmer the wire may be compared to the air around the freezing point.

  • $\begingroup$ Given many power lines get encased in ice, and that is what brings them down often in winter, then the heating effect must be minimal... $\endgroup$ – user207455 Jun 3 at 8:43
  • 1
    $\begingroup$ @SolarMike Certainly. Otherwise the power losses would be enormous. However, if a wire is warmer than the air, say, by one degree, the wire would still get iced in a cold weather, but at a moderate ambient temperature birds perhaps may feel the difference? $\endgroup$ – safesphere Jun 3 at 8:49
  • 1
    $\begingroup$ In my region in Greece all high voltage lines are encased for the fear of fires from tree growth etc. The birds still sit on the wires, and also on the telephone wires which carry very little current. $\endgroup$ – anna v Jun 3 at 9:36
  • 1
    $\begingroup$ This question (v2) seems to be more about natural habitats for birds than physics. $\endgroup$ – Qmechanic Jun 3 at 10:24
  • $\begingroup$ Apparently, monitoring the temperature of transmission lines is a thing, so that would imply a "maybe". nktphotonics.com/lios/en/application/…. $\endgroup$ – rghome Jun 3 at 10:29

According to the physics of electrical systems, no, not really. The line and the area around the line may be a couple of degrees warmer, but this is not the reason they do it.

According to the Audubon Society, there are 3 reasons for birds to sit on telephone and power lines.

  1. It allows them to see their surroundings and keeps them safe from most predators
  2. It allows them easier take offs.
  3. The lines are easier for them to grasp and sit on.

Your question is not as easy to answer as you might think.

A typical light industrial plant power line is 13,500 volts. Its amperage is dependent on the entire system from the time it was generated through the power line impedance, plus what the line is capable of holding. The system is designed to have as little loss as possible. (loss = impedance) impedance generates heat.

High voltage power lines can have up to 750,000 volts on them.


Your Answer

