Fairday's Riddle: Branching Out...

Hello, Riddlers! Can you guess our theme? I found a discarded one and incorporated it into a rock garden I've been building— spot it in the clue? ~ F

Set high, twigs and bits, guarding that which fits and sits. Peeps waiting for their flight call on mom to bring a bite. Tucked in safe, living free, mostly found in a tree. 

What am I referring to? Stop by Friday for the answer. 

I gave you a clue! (