I don’t understand something. If there is an explicit mishna in the Yerushalmi in Chullin (3:6) to rely upon describing signs of a bird, why would there be any disagreement about the stork, including according to Rashi? Either it has the signs or it doesn’t, as indicated by Rabbenu Yerucham. On the hand, why do poskim disagree about the names and identities of birds when they can simply rely on the simanim? Thank you.
Please see the following link http://dinonline.org/?p=48225&preview=true which should answer your question.