Mimicking Birds – Subsonic Words chords

According to live performances, it seems Nate plays the chords like one would play Em 
and Am in standard tuning, except he clearly plays in a lower tuning.

As far as i can tell it is CGDGBD

A11? Am9/A11?D|---x---------0----|B|---0---------0----|G|---0---------2----|D|---2---------2----|G|---2---------0----|C|---x---------0----|
The strum pattern is basically down down up, down down up, down up (listen to the song for clarification). I would love some help figuring out the leads and bridge!
Please rate this tab: