I believe it to be 'Fleas' by Ogden Nash
The caged bird singswith a joyous songof the captive life that kept it safe all along.This answer exemplifies the two birds: free and caged. Free in such a way that it is able to sing a song of its choice, and caged, because even if it is in captive it has something to be thankful for, its safety.
Answer:
water?
Explanation:
Hope this helps and is right
A comma after an unfamiliar word