Why Do Birds Gather To Sit On High Tension Wires In Cold Weather?

I suppose in the summer, birds seek shade and protection in the trees. They are local birds and know where the food and water are. They often defend their territories and will not allow other birds to come too close.

In the fall, they are probably migrating birds, just taking a rest stop on their way to the south. So they perch on the highest and most visible spots to attract their own kind to regroup for the next flight. You can see far higher density and they come in waves upon waves out of the north.

Interesting question. Hope someone can shed light on this.

This is a guess but the electricity may keep them warm or something

Probably the birds need a shaded place to sit in the summer,when the weather is quite hot. I have also noticed this phenomenon in the third world countries,where the electricity wires and the polls are found along the roadside. The birds sit on the wires for long in the winter. These wires are made of copper,with plastic as insulator. They are always quite hot due to electricity conduction. Your point seems right to me that the birds want some heat and energy from these high tension or heat conducting wires.

I believe that some spans of wire have more resistance than other locations, and, as a result are warmer than other locations.I think that is why we see birds roosting on the same locations during the cold months.