I've been looking at these. Not to keep squirrels out but to keep starlings out.
I don't mind feeding the starlings, but they are the 'yobs' of the garden; squabbling and fighting with everything else and each other, scoffing everything, and pushing all the other birds away from the food. All other birds in the garden seem to get on with each other - even forming well behaved queues to take their turn feeding (apart from the blackbird pair who won't tolerate other blackbirds).
I've been put off getting one as:
A. I'm not convinced birds would effectively put themselves in a cage.
B. I don't know if they would even keep starlings out.
This is the type of thing I was looking at; a feeder with an outer cage:
Thoughts, peeps?