Rook

Filled up the feeders this morning and only the Rooks keep coming. I'd like to know how I can keep them away so that the little birds get a look in. I only put seeds for little birds in the tray but the Rooks just gobble the lot. Horrible dull and cold here today.  Only bight thing is that the cat from No. 6 that has been missing for two days has turned up looking fit and well!