It's Ben Weatherstaff's robin.

He's buildin' his nest.

He'll stay here if us don't fight him." They settled down softly upon the grass and sat there without moving.
"Us mustn't seem as if us was watchin' him too close," said Dickon.
"He'd be out with us for good if he got th' notion us was interferin' now.

He'll be a good bit different till all this is over.

He's settin' up housekeepin'.