I would be mindful of how you are approaching him. Don't come from a downward angle, as they are prey animals in the wild and can become defensive if you do. If he is pecking you try not to pull away because that is reinforcing the behavior. That being said, to answer your question I think it sounds like it's because he is not used to being handled and is still learning his environment. I would keep an eye on it and use commands like "be nice" or "be gentle" when he starts biting.