So, the crows are technically a "weapon" of the demon Malphas. His power involves creating weapons. He was able to somehow create a way to summon and control the crows. I don't believe he, himself, is the demon, or a demon, he just has the ability to usurp the demon's power.
Still, this is interesting in that his main weakness is the fact that he can't wield the weapons he can create. These crows, however, prove that he can very effectively use "weapons" that are not wielded. If there are more indirect "weapons" like these crows out there, then this guy is definitely more of a powerhouse than we gave him credit for.