Jamieson, Fausset and Brown on Deuteronomy 32:11

11. As an eagle ... fluttereth over her young--This beautiful and expressive metaphor is founded on the extraordinary care and attachment which the female eagle cherishes for her young. When her newly fledged progeny are sufficiently advanced to soar in their native element, she, in their first attempts at flying, supports them on the tip of her wing, encouraging, directing, and aiding their feeble efforts to longer and sublimer flights. So did God take the most tender and powerful care of His chosen people; He carried them out of Egypt and led them through all the horrors of the wilderness to the promised inheritance.