Your cat must be an amazing hunter if she can catch birds that easily ! Birds are pretty hard to sneak up on, unless there is a bird feeder where they are coming and eating and the cat sees them and catches the birds while they are eating.
I think the cat bell would probably stop her from catching the birds; but as was mentioned, it would stop her from catching mice or any other prey as well.
I don't know if it would work, but they make little glue-on toenail covers to keep cats from scratching up furniture, and maybe a set of those would also stop her from grabbing the birds.
Except for keeping her in the house during the day when the birds are out flying around, it is going to be pretty hard to stop her from trying to catch them. But if you keep her in during the day and let her out overnight, she can still catch mice and other night creatures, and the birds will all be high up in the trees sleeping and safe by then.
