Was Smaug woken up by a nut hitting the mountain?

I have been re-watching The Hobbit: An Unexpected Journey. By the end, the movie shows a how a bird came knocking (actually hitting a nut) on the mountain. And then there is shifting inside, and Smaug awakens and opens his eyes.

My question is: was his awakening due to that small sound? If so, how was Bilbo supposed to have any chance?