So mastered by the brute blood of the air,(line 12)
The word "brute" means beastly or animalistic – think of the word "brutal." But the "brute blood of the air" also makes the air sound like a supernatural being, a living force of nature with its own metaphorical blood. Even the air conspires against Leda in Zeus's favor.
Did she put on his knowledge with his power Before the indifferent beak could let her drop?(lines 13-14)
Even animals have power, and animals are usually considered to be "lower" creatures than humans. The speaker knows that Leda understands the swan's power – how could she not? – but he's curious about how much she understands of its supernatural being. Does she know that the swan is really Zeus? Did she take on or "put on" some of Zeus's omniscient knowledge? Or did it all happen too fast?