Tell me now, without a frown. What grows up while growing down?

Even though we sing that its days are over, Every one has its day. Maybe that’s why they’re so beloved A bestie always up for a nap, drive, or play.

Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see. What am I?

In my bosom a drum does play, a rhythm that guides the night and day. Oh, my dear, it's quite the feat, the steady pace of life's own beat.

Tell me now, and don't be late. What kind of bird can lift the most weight?