Wildrose, my guess would be the squirrels...they do eat rhododendron and azalea buds.

Here in PA it would be deer. They can't bite things off, they rip them off. This is usually the telltale sign of deer damage. Last spring I planted 20 deciduous azaleas. The deer removed all the big fat buds the next night. I now have a deer fence around the azaleas. I protect my rhododendrons from deer with deer netting. It must be removed before the flowers open and the shoots start coming out or the plants grow right through the netting and it does no good. I just use it for winter protection. Except for my azaleas, I only have deer problems in the winter and early spring after the first snow.

There are many repellents that will work for a while. They need to be reapplied after rain and periodically even if there is no rain. I have a section on my web site about deer and rhododendrons.

Regarding the other critters. Rabbits will try to eat anything, even a garden hose. But they can't reach very high. Squirrels usually chew the buds off. They may miss some that they chewed off. There are birds that like rhododendrons flowers. One is the Blue Tit in the UK. I don't know of any here. I don't think raccoons or cats would do it. Rhododendron buds are toxic to many animals.

Here is a link that might be useful: Henning's Rhododendron & Azalea Pages

oops! did not notice your other post about this before replying. still thinking squirrels.

Deer jump fences unless they are over 7' tall.