I mastered my high so I'm bucking at the birds

from Common – Soul Power Lyrics on Rap Genius

Meaning

he’s mastered his high to the point that his literally at eye level with the birds.
Also its a homage to the recently released(at the time) track by the roots “water” from the album phrenology, that was recorded around the same time.

http://www.youtube.com/watch?v=rIUVcESFnt4

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