They naturally visit your lawn periodically (at least here in the western U.S.) looking for insects and seeds. They find the seeds and other birds see them feeding and the dinner bell has rung. birds can eat just about any seed it can swallow. Since birds don't have stomachs, but rather, craws that are filled sith small stones and sand they find along road sides and such, the seeds are ground into mush before entering their digestive system...
A friend down the road from our ranch, planted a fairly large new lawn. The bids arrived in droves. Another friend told him to take a tennis ball or some other ball of similar size, paint two prominent eyes on it and lay it in the newly seeded lawn. He says it works very well... the thought being the birds think it's a snake... Haven't tried it myself... Best of luck!