I came across this post from one of my favorite rescues about double shepard's hooks hurting animals, and I hadn't heard about this before so I thought I'd share.
Beware of the dangers posed by shepherd's hook bird feeder poles! Every year, rehabilitators rescue countless birds and squirrels that become ensnared in the V- shaped gap between the two hooks. In their frantic attempts to escape, these animals often sustain serious injuries.
You can easily prevent these tragic situations by removing the second hook and opting for a single-hook pole that eliminates any V-shaped joints. Alternatively, consider wrapping the narrow joint with cloth, vet wrap or self-adhering tape (without adhesive) to mitigate risks.
Narrow gaps can become deadly traps for wildlife. Birds and squirrels, eager to reach feeders or other items, can easily get their legs or feet stuck in these tight spaces, resulting in painful injuries or even death. By taking some simple precautions, you can protect the beloved wildlife in your yard from unnecessary harm.
One person in the comments suggested JB Weld as a more permanent solution.
I don't have the hooks, but I always want to keep my bird buddies safe. If you guys use them, you may want to consider critter proofing your hooks.
You can get window adhesives to prevent birds from flying into them. I have one window that used to be really bad for it but since we put the bird collision prevention stickers on it we haven't had a single one smack into it.
Just remember to put the sticker on the outside as it's meant to break up the reflections on the window.
Is there anything that uses colors that birds can distinguish but we can't?
I'm not sure, I was looking for something inexpensive and quick to install at the time and the stickers fit the bill. There might be something out there, maybe someone else will have a better answer for you.