Some time ago I bought some thick sisal rope and finally had the opportunity to use it: it stretches from one side of the room to the opposite wall.
The tiels are crazy about it, not only perch on it but they love to pick at those tiny hairs that sisal is made of.

Well, all nice and good, everyone's happy... NO!!! Mr Darcy managed to get his head stuck into a tiny hair loop. Basically these hairs sometimes remain attached to the main rope on both sides, creating a little loop. I am sorry I can't explain better, I will post a picture as soon as I can find another one of these loops.

I was wondering if any of you who use sisal have seen anything like what I am describing.
Fortunately we were all in the bird room at the time of the accident so Darcy got freed immediately, but I won't feel safe until I have replaced that rope. Shame because it wasn't exactly cheap!

It might be possible to rehabilitate the rope and make it safe. You can prevent tangling problems by cutting off any loose ends or loops that are more than an inch long. Then check it daily and supervise for a while to see how long it develops new loose ends - if it happens in a matter of minutes it's goodbye rope, but if it take a long time you can decide whether you feel safe using it.

That's a good idea, thank you! I will check it concentrating especially on two spots, one very used and one not used at all. I want to see whether the problem develops where they play or it's just something that happens to the rope by itself.

It's probably from the birds, I doubt that the rope would just unwind itself. You said they liked to pick at it, and there's a safety issue if they can pick out a long strand in a short period of time.

I've had no trouble with sisal rope, but then my birds don't really chew on it.

Why dont you try just making a cut on the loop just so that its not in a circle shape so that the birds heads dont get stuck, but they can still get some fun by chewing on it.

The problem is that the birds are probably creating the loops by tugging at the rope fibers and pulling them partly loose. The question is how quickly they can do it. If they can create a dangerous situation in a few minutes when no one is looking, that's a problem. If it takes them hours to do it that's not as dangerous, because frequent monitoring will catch it before it becomes too hazardous.

Hmm, this is tricky. Give me some time, ill come up with an idea,

Yes. that's the problem. They don't really chew on it. they just preen it. I am checking it every time i'm around, no loop has formed yet.
Maybe they will get tired of preening it and just use it to perch sooner or later. I am adding new stuff every day so they start having some better choices to entertain themselves... hopefully!