Birds
"Birds" represent rational concepts in the external man and intellectual concepts in the internal man.
Vine shall give her fruit, and the ground her increase
In Zechariah 8:12, 'the vine shall give her fruit, and the ground her increase,' signifies that the spiritual affection of truth produces the good of charity, and the natural affection of good and truth produces the works of charity.
(References: Apocalypse Explained 695)