How do you get a Large egg on Harvest moon DS?

The more hearts a bird has, the larger egg it can lay. You can increase your affection with your animal by leaving it outside, picking it up and down, and by using the Touch Glove to pet your bird. If you use the Touch Glove you can reach a Red Heart in the petting mini game with a score of 9000 with a chicken, and 6000 with a duck.