>>3152534 (LB)
Birds sing for many reasons, but when do they usually stop singing aside from them being asleep?
When there's a predator.
If you ever use a hawk or an owl call, watch how quiet the forest gets, you won't hear a single song.
And then moments pass by when things are all clear, they go back to singing.
Maybe Q is saying the birds started singing because the bigger birds aren't in the forest anymore.
Well, at least in the sense the bigger birds that were keeping them quiet, now they have nothing to lose by singing.