Albert Barnes Commentary Job 39:27

"Is it at thy command that the eagle mounteth up, And maketh her nest on high?" — Job 39:27 (ASV)

Doth the eagle mount up at thy command? – Margin, as in Hebrew, “by thy mouth.” The meaning is that Job did not have power to direct or order the eagle in his lofty flight. The eagle has always been celebrated for the height to which it ascends. When Ramond had reached the summit of Mount Perdu, the highest of the Pyrenees, he perceived no living creature but an eagle which passed above him, flying with inconceivable rapidity in direct opposition to a furious wind (Edinburgh Encyclopedia).

“Of all animals, the eagle flies highest; and for that reason the ancients have given him the epithet of “the bird of heaven”” (Goldsmith). What is particularly worth remarking here is the accuracy with which the descriptions in Job are made. If these are any indications of the progress of the knowledge of Natural History, that science could not then have been in its infancy. Precisely those things are mentioned here which all the investigations of subsequent ages have shown to characterize the classes of the feathered creation referred to.

And make her nest on high – “The nest of the eagle is usually built in the most inaccessible cliff of the rock, and often shielded from the weather by some jutting crag that hangs over it” (Goldsmith). “It is usually placed horizontally, in the hollow or fissure of some high and abrupt rock, and is constructed of sticks five or six feet in length, interlaced with pliant twigs, and covered with layers of rushes, heath, or moss. Unless destroyed by some accident, it is supposed to suffice, with occasional repairs, for the same couple during their lives” (Edinburgh Encyclopedia).