No one is going to win this debate, because there's no way to know. There are people in certain situations, like a war for example, where a human may dispose of a loved one's body and move on very quickly because they must for their own survival.
Who knows what goes on in a bird's or any animal's brain? Who knows what goes on in a human's brain? What exactly is the definition of grief or any emotion? The only way we think we know a human is experiencing a particular emotion is their outward behavior, if an animal has similar outward behavior how does anyone know the cause?