If the birds are staying because they like it, or have some special "bond" then why clip them at all? Clearly they can't fully fly as they would naturally. It doesn't add up.
Most birds are social animals (including Ravens) and prefer to stay with their flock (which includes caretaker humans), so it's not really about making sure the birds are kept prisoner. Pet birds will occasionally fly away because they're spooked (e.g. from a bird of prey) or get lost. Once they've flown far enough away, you're likely not to see them again. [0][1]
There are those who free flight their birds, but that requires lots of training and requires constant monitoring of the birds, calling out to them when they get too far. Birds rely on loud calls to find their way back to their flock (hence why they squawk all the time--its a natural homing beacon meant for large distances).
I'd say semi-clipped wings are probably a good compromise without constant monitoring. These birds will outlive birds in the wild, while still having a greater degree of freedom.
Those are all excuses to justify keeping the ravens captive because of a ridiculous superstition. The only ethical thing is to not keep these birds and let ravens (and all birds for that matter) live their lives naturally in the wild.
I could chain you up "just a little" and let you have a walk now and then and even feed you well and treat you nicely, but you would still be a prisoner and it would be wrong for me to do that to you.
There are those who free flight their birds, but that requires lots of training and requires constant monitoring of the birds, calling out to them when they get too far. Birds rely on loud calls to find their way back to their flock (hence why they squawk all the time--its a natural homing beacon meant for large distances).
I'd say semi-clipped wings are probably a good compromise without constant monitoring. These birds will outlive birds in the wild, while still having a greater degree of freedom.
0. http://www.libertywings.com/2008/training/basic-flight-train...
1. https://adventuresofroku.com/blogs/education/free-flight-tra...