My aborvitae leafs are dropping significantly. There are still green. They do not have evidence of chewing like from squirrels all though we have quite a lot of them since a neighbor regularly feeds them.
Macomb County Michigan
The squirrels could very well be the problem. They trim twigs for nest building and drop many. They also go after the cones. Unlike the damage from deer or rabbits, squirrels may be higher up. Control of squirrels can be tricky. Local ordinances may limit what can be done (i.e. shooting, trapping, poisoning, et al.). Repellants may not be effective.