Grackles have discovered the bird feeders. They may also have a disk at the bottom where the birdies can also stand. One can, I apprehend, spend quite a bit of money on a solidly constructed feeder complete with features which the birds are quite indifferent to but which justify the vendor of feeders asking for outrageous sums of money. Your basic inexpensive bird feeder, however, consists of ramshackle bits of plastic which snap together. As I say grackles have discovered the bird feeders.
Grackles are very agressive in their feeding habits.
They are also somewhat heavier than the finches and sparrows. They have discovered that they can dislodge the bits of snap-in plastic that serve both as seed dispensers and perches. From their viewpoint this is advantageous - the bird seed pours out. Yours truly is not so happy with their discovery. Since the grackles have discovered that the span-in perches can be made to snap out I have endeavoured to emplace them more securely.