Mika but there is a round net suspended under the big feeder that catches most of the seed that the birds drop, so the squirrels have plenty of seed to eat without raiding the feeders. The sparrows are especially bad about throwing seeds out. They seem to eat about 1 seed in 10, and sometimes there will be a flock of 5 or 6 sparrows around at once.
My cat found it amusing to stalk the birds foraging on the ground so we came up with the catcher idea, and that has made everyone happy (except the cat, who is really too old and slow to catch birds anyway). Here's the feeder, net catcher and the cat, too since she was out there posing. That feeder is a fancy "Squirrelbuster" designed to shut the ports if a squirrel gets onto the perch ring. It works except for a couple of the younger squirrels who are light enough that the ports don't close all the way, so they can get their little paws in there and scoop out seeds. They only do this if the net is empty, though.
