Board Thread:General Discussion/@comment-27994404-20200219161151/@comment-24018437-20200219213020

Exactly. For a lack of better explanation, think of Qrow and Raven not as true birds, but rather bird-shaped humans when they shapeshift. The level of emotions, intelligence etc hasn't changed, its just their body. Thus, the Grimm would (if this theory is correct) detect them as humans based on those.

Meanwhile, a real corvid would be ignored because they don't detect the strong emotions that come from them being humans.

Honestly, the real question is this: if the God of Darkness created the Grimm to destroy all life and creation before humans were created, thus meaning they did attack animals and plants, why did they stop doing that and focus purely on sapient creatures?