Are you still having problems with grackles, laleo?
It might be too soon to tell, but I may have seen the last of the invasion. I took my solar feeders down for a little over 2 weeks, and cleaned up any remaining mess under the feeders that could tempt the grackles into sticking around. I waited until I stopped seeing them in my yard at all; they even got discouraged enough to stop coming to the bird bath.
Then I put my feeders back out, but I decided to try a seed by Morning Song called Finch & Chips (love that name!) I should probably be putting it in a finch tube feeder with tiny holes, but I just wanted to give it a try to see how it would go over. The Finch & Chips is nyjer seed (which grackles don't like) mixed with tiny chips of hulled sunflower.
So far, so good! All of my little birds returned the first day (except for my goldfinches, they must have migrated?) and have been enjoying this food. And there's hardly any mess under the feeders because the sunflower chips are tiny enough that the little birds aren't wasting any. (With whole sunflower hearts, the birds would take a kernel and start eating it, but 1/2 to 3/4 of the kernel would fall out of their beaks onto the ground). So there's nothing on the ground for the grackles to really peck at.
I've noticed a couple grackles so far at the feeder, but they have a really hard time perching. They have to sort of cling and flap their wings madly at the same time to hold on. With the whole sunflower kernels, they could manage to fill their beaks full several times before hopping on the ground to take a break before doing it again. Now they are avoiding the nyjer seed, so they have to work very hard to cling and pick through the seed for the teeny bits of sunflower. It must be too much work, because I hardly see the grackles at all, and they aren't getting aggressive and guarding "their" feeder because they just don't seem interested.
So I'm crossing my fingers that the invasion doesn't return to drive away my little songbirds!