Why does the Torah refer to the ostrich as "Bas ha'Ya'anah"?
Chizkuni: Because the flesh of a full-grown ostrich is hard and inedible.
Why does the Torah say "Bas ha'Ya'anah"?
Chulin 64b: This forbids the eggs of a Tamei bird.
Riva, Moshav Zekenim, citing Ri: An ostrich eats iron; when it is mature, it is hard like iron, and people do not eat it. Its young are proper to eat.