Electrified Birdfeeder?

A squirrel weighs much more than a bird. When you get your zapper going, set it off by having a microswitch turn on when the squirrel jumps on the bird feeder; that will turn it on and zap the squirrel. No need to play sentry.

How to do it? The bird feed could be attached to a spring that it hangs from. When it stretches due to the squirrel weight, the micro closes. The details are up to you.

Unless, of course, you're using your bird feeder to feed vultures ;-)

Al

I'd need to know how your bird feeder is supported and how the squirrels are getting onto it.

There's an outfit that makes a 'squirrel centrifuge'. A bird feeder with a weight sensitive switch, motor and battery that spins and throws squirrels off when they climb on it.

This is a question that is asked all the time. Birders have known the solution since long before anybody knew anything about electricty. Make what you offer the birds unappealing to mammals.