"Birds" represent rational concepts in the external man and intellectual concepts in the internal man.

7. It Is the Lord's Divine Nature That Makes Heaven

While we call the total assemblage of angels heaven because they do make it up, what really makes heaven overall and in every specific instance is the divine nature that emanates from the Lord, flowing into angels and accepted by them. The divine nature that emanates from the Lord is the good intrinsic to love and the truth intrinsic to faith. The amount angels accept from the Lord of what is good and what is true determines the extent to which they are angels and are heaven.