Storks are harbingers of spring and enemies of snakes. The stork as a Christian symbol represents holiness and vigilance and it is symbolic of the Annunciation of the angel to Mary.
The association of storks with filial love is also found in the myth of storks delivering babies (something that seems to have its origin in the migration of the bird and on the fact that it is also a symbol of fidelity and monogamous marriage, since storks are widely (but fallaciously) believed to mate for life).