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

'Forty' represents completeness because 'four' and 'ten' both mean what is complete. Forty is the product of four and ten. Compound numbers have a meaning similar to the simple numbers which compose them, and all numbers in the Word represent spiritual realities.

(Odkazy: Arcana Coelestia 9437; Exodus 24:18)