Thank you all for the encouraging words. I took some more pictures in this same fashion which had some really nice 'silhouettes' of the individual blurds but none were as mesmerizing as this where they all make a clean sine wave like pattern across the image.
Frank, I think what you are seeing is an optical illusion from some of the birds dipping below the horizon. Scroll the image down so that the horizon is at the bottom edge of your browser and compare, looks straight to me.
Thanks again.