"Puffed out" is actually a nicely creative way of saying this. Other creative choices are possible: "flung," "thrusted... sideways," "jerked," "popped," "quivered," "lifted," "spread."
Each of these requires modifying words, thus:
"They jerked their wings in and out, making tiny balancing movements."
"Their wings popped slightly up and and quickly down again, trying to keep them steady."
And so on, and so on. ("Spread" is of course the classic choice when used to describe a bird's wings opening, and you can use it effectively if you modify it carefully.)