Most Helpful Girl
Interesting. I think "sometimes all our thoughts are misgiven" relates to the previous rhyming group, which is
"There's a sign on the wall
But she wants to be sure
'Cause you know sometimes words have two meanings"
So I think he's saying that words are often ambiguous, so sometimes all our thoughts just fill us with fear unnecessarily. I think the songbird is meant to suggest that sometimes people just talk to hear themselves talk, like the songbird sings just for the sake of singing.
Most Helpful Guy
I always thought this song as a sort of metaphor of a transition from the past to the future.
Personally, I think it means the latter.