spiral metallic objects on phone lines

[#1]

on a street near where i live there are spiral metallic objects on the telephone lines. they are on some overhead lines, but, not all.
Are these for keeping birds off, or to cut down on interference? I will go and take a photo if anyone needs more clarification what they look like. I'd do it now, but its raining quite hard.
Ive googled on google images but cant find anything. Its just perplexing me what they are.

[#2]

if you live near a river they may be the one they uses to stop swans and other water fowl from colliding with the cables.

[#3]

nearest river is about 1 mile away, dunno it could be for that, cos i have heard geese flying overhead.
gonna go and take a photo tommorrow and post up.

[#4]

I always thought they were for stopping a harmonic resonance setting up in the wind. (but I could be totally wrong)

[#5]

Quote

I always thought they were for stopping a harmonic resonance setting up in the wind

could be, but, surely these would be fitted to all the phone lines and not just a few. there are a few placed about 2 meters apart on it seems random lines from the pole.

[#6]

Whether a line was susceptible would depend upon the length and the tension. I'd guess they'd only fit it to the susceptible lines.

[#7]

Do you get a lot of birds in your area. They are normally fitted where large birds exist or if you are on their migration route to stop them hitting the cables.

[#8]

Any pidgeon lofts in the vicinity?  All those round here have them fitted on their nearest wires.