To begin with, fill your feeders with their favorite seeds. I have always provided the migrants with black oil sunflower seeds. They are also fond of safflower seeds and raw peanuts. While I have never served up either seed to northbound migrants, my daughter fills her feeders with both sunflower and safflower seeds. This year, the birds visiting her yard have shown a preference for safflower seeds. On the other hand, I have not seen a grosbeak in my yards this spring.