The choking noise he makes is probably intended to be a laugh. It's definitely a laugh from how Garrus' shoulders shake and his head bows. His whole body shakes too. Clearly, he's trying not to burst out laughing, for Koby's sake.

"Power puberty?"

Oh that just, set him off again. His feathers rippling white, the eyes along his collar brightening to painfully clear blue.

"It's - It's possible."