Clawstring is the main disease for pigeons. Human made threads, string and actually most of the time it's human hair that wraps around the toes of the birds. When it's not removed, it gets tighter, and eventually cuts off the blood supply. This will lead to the toes dying off.

To solve this issue some human intervention is required. The bird needs to be caught and the string removed. I use a pair of nail scissors that I carry on me. In some cases, when the toes have completely swollen, it has gone passed the point of cure. The threads will be deeply embedded in the flesh and it can't be properly removed, unfortunately.

Birds can still have a good life with a couple of toes missing, but life will get harder, and they might start to limp. This obviously has adverse impacts on their competitiveness and procurement of food.