So you're agreeing with me?
If you're a low-refresh shifter, you may very well be able to assume the form but mechanically you're not going to gain the full benefit. In-game that plays off as "I'm not actually a bird, so I have to figure out how to fly".
Personally, I would probably just allow the person to fly regardless of having the ability on the sheet (he is a bird) but I would prevent it from being a true advantage mechanically. If someone changes into a wolf, they're still going to be able to run even though it's four legs. They might not be very graceful is all.
It's all a good opprotunity to roleplay that origin story and sense of discovery.
@Mr. Death
But were weren't talking about an emu, where we? In there case, flight isn't an essential part of their nature (obviously). For a raven, it is - though for a human transforming into a raven maybe not so much.