By them shall the fowls of the heaven have their habitation, which sing among the branches.
All Commentaries on Psalms 104:12 Go To Psalms 104
Augustine of Hippo
AD 430
14. Then the Psalm goes on in its text, "Upon them the fowls of the heaven shall inhabit"(ver. 12). ...Upon the mountains, then, the fowls of the air shall have their habitation. We see these birds dwell upon the mountains, but many of them dwell in plains, many in valleys, many in groves, many in gardens, not all upon mountains. There are some fowls that dwell not save on the mountains. Some spiritual souls doth this name denote. Fowls are spiritual hearts, which enjoy the free air. In the clearness of heaven these birds delight, yet their feeding is on the mountains, there will they dwell. Ye know the mountains, they have been already treated of. Mountains are Prophets, mountains are Apostles, mountains are all preachers of the truth. ...
15. But think not that those "fowls of heaven" follow their own authority; see what the Psalm saith: "From the midst of the rocks they shall give their voice." Now, if I shall say to you, Believe, for this said Cicero, this said Plato, this said Pythagoras: which of you will not laugh at me? For I shall be a bird that shall send forth my voice not from the rock. What ought each one of you to say to me? what ought he who is thus instructed to say? "If any one shall have preached unto you a gospel other than that ye have received, let him be anathema." What dost thou tell me of Plato, and of Cicero, and of Virgil? Thou hast before thee the rocks of the mountains, from the midst of the rocks give me thy voice. Let them be heard, who hear from the rock: let them be heard, because also in those many rocks the One Rock is heard: for "the Rock was Christ." Let them therefore be willingly heard, giving their voice from the midst of the rocks. Nothing is sweeter than such a voice of birds. They sound, and the rocks resound: they sound; spiritual men discuss: the rocks resound, testimonies of Scripture give answer. Lo! thence the fowls give their voice from the midst of the rocks, for they dwell on the mountains.