Albert Barnes Commentary Psalms 104:12

"By them the birds of the heavens have their habitation; They sing among the branches." — Psalms 104:12 (ASV)

By them shall the fowls of the heaven have their habitation—Among them the birds of the air dwell. That is, among the trees which spring up by the fountains and watercourses. The whole picture is full of animation and beauty.

Which sing among the branches—The margin, as in Hebrew, notes: “give a voice.” Their voice is heard—their sweet music—in the foliage of the trees which grow on the margin of the streams and by the fountains. There is scarcely to be found a more beautiful poetic image than this.