a) those who fly by sake of their feathered wings;what type of birds do you know?
b) those who lay, cooked, in a dish.
Btw, in my regional dialect, oseo (pl. osei), other than 'bird' means 'dick' and this brings to my memory a scary episode.
In high school, my English teacher was a German lady (guess how fine an English I could have learnt ...).
One day, dunno how, she was in a critic mood towards regional cuisine and stated "I don't like polenta! How can anyone like such a thing?"
Then I raised my hand and asked "c'mon Madam, don't you like osei??"
That time my mom had to come and explain to my school's Principal that I wasn't a pervert but just an idiot.