I cheated. You'll note all the birds are exactly the same. Digital trickery. I don't care. It was late, just before nighty-night. For some reason, I wanted a picture of a flock of birds1 against a blue sky, and I got what I wanted. All is fair in love and drawing.
1 I specifically wanted swallows. I wasn't referencing a picture, and the tail is a bit off, but they do have a general swallow-ness about them.