yar,, kittens are quick learners,,
you shoo them away a few times max a week they know enemy is approaching and they'll know the drill.
Consider the ULTRA SOUND PET ALARM.
This device is similar in that it can emit an Ultra
Sound when animals get within a certain range. However,
it also has an "Audible" setting so that people can
hear when an animal enters a restricted area. This
unit does not need a transmitter to actuate its alarm;
it works off motion and has both a "low" and "high"
setting. It is great to use on countertops, doorways
or automobiles. Cats will be frightened by its sound
and immediately leave areas where you have it installed.
This is a great device to use when you want to keep
cats off a certain surface, out of a particular room
or away from a certain area in the home. They work
off a 9 volt battery and have an effective range
of 2-8 feet. However, some cats are pretty
stubborn and may need a bit more persuasion