A large British study found that five farmland songbirds preferred wheat to oats and oats to barley. But tree sparrows and reed buntings preferred maize to all cereals except wheat, while house sparrows preferred maize to all cereals. On the other hand, corn buntings and yellowhammers preferred all cereals to maize, although neither is exactly a common garden bird. All species preferred cereals to sunflower seeds, which I have to say surprised me, given the rate at which the birds in my garden consume sunflower seeds. I suppose none of the birds in this study were finches, which have a well-known preference for oily seeds. So, although sunflower seeds are strongly promoted by bird food suppliers, perhaps the best advice is that if you have room for two feeders, filling one with oily seeds like sunflower, and the other with starchy seeds like a wheat/maize mixture (which is also cheaper) will attract the biggest range of birds.