I have nothing against birds and the feeders that help them survive. However, I do wish bird lovers would consider the health of their living trees when installing bird feeders.
Once the Katsura tree (Cercidiphyllum japonicum) "swallows" the string, there is no way to correct the situation. The girdling that occurs leads to two huge problems: 1) water and food transport are limited and eventually completely cut off. Then the branches die.
2) The other problem is failure at the point of constriction.
In the above example, only one branch is affected and it's already dead. I couldn't really cut it off because I didn't want to deal with relocating the bird feeder. I suspect the branch will eventually fail. Then the owner should consider other ways of hanging the bird feeder.
Definitely help birds in your garden but don't forget about girdling and the death it causes.
Vas Sladek, B.Sc., CLT