The birds of the air do GOD's bidding. ~ Reference (1 Kings 17:4-6)

God ordered ravens to feed Elijah at the Brook Cherith. The ravens brought found to Elijah day and night. God could have sent angels to deliver food to Elijah, but chose to use mean creatures instead.  

God has control over the mightiest and the smallest creatures, and can use them as He pleases to accomplish His purpose.