Maria and her Mom noticed doves landing on their fence each morning. They wanted to feed the doves but they were not sure what the doves liked to eat.

They collected an assortment of food:
bread crumbs
bird seed
sunflower seeds
peanuts
For four mornings, they threw out one kind of food. Then, in the afternoon, they checked to see how much food the doves ate.
What would be a good question for Maria's investigation about doves?