What Is It?

Assuming that you are referring to the wire along the top. my guess is that it is to make birds very uncomfortable when trying to perch on the bar and thereby causing them to deposit their droppings elsewhere. It doesn't appear to be totally successful going by the dropping on the top rail there.

The wire appears to be too high to be a real deterrent.

My own version has two wires set lower, and still some very persistent avians attempt to do a balancing act on the wire, but fail to get steady enough to attend to business.

Oh, I see. I thought it was some kind of safety wire ( to keep small children from crawling between the bars)

Looking closely at the white vertical stain just to the left of the upright post on the top rail, and the corresponding white puddle below it on the bottom rail, I'd say it isn't 100% effective.

You may have missed where I made that exact point in the last sentence of the first paragraph in my post.

The wire is too high to prevent any but the larger birds from alighting on the rail. While that may mitigate the size of the stains, it will still get deposits.

I'm not disputing anything you said.

It may not be 100% effective, but,... its also relative compared to what it was without it.

If they had Farmers Insurance, we might have 30 second spot.

At least the windows were rolled up...

Agree, this appears to be a Birdwire system.

Bingo! ....pidgeon perplexer...

Just wondering if it might be more effective if used as a "slack-wire" rather than a "tight-rope".

Maybe it's not to deter birds from sitting on it but people?

Could be... shortwave radio antenna.

The first thing I looked for was a signal wire connection.

Then I thought maybe it sent out a vibration.

At the end poles, the wire is looped, tied to itself with a fishing knot. A very small/short spring is attached one side to the wire loop and on the other, a loop on the stainless steel post.

I think you're right, it's a bird deterrent. The mailboxes in our neighborhood have the house numbers on top and tend to get "decorated" by birds perching there. We solved the problem by buying a rubber toy snake at the local zoo gift shop and leaving it on top of the mailbox.

We have had people come to the door to tell us about the snake on our mailbox. I guess they didn't dare venture close enough to see that it wasn't real.

My wag is that when the wind blows these wire cable rails create sound that acts as an animal deterrent...probably to keep them out of a construction project....and/or to keep people from wandering into the area....

Just ‘The Man’ trying to keep us down...

Thanks for this.

My house is plagued by pigeons, which sound like much larger animals running around on the roof. I was planning to install bird spikes or gel, but this looks like a much simpler solution.

It looks like a golf course in the Middle East after the sprinkler system has been non-operational for weeks.