It’s certainly a challenge to photograph birds in flight. Your shutter speed must be fast enough (1/1000 second) and your depth of field sufficient to keep the birds in focus (f/20), as they won’t stop for you to capture your photograph. I used an ISO of 800 on a bright sunny day, to allow me to shorten the shutter speed and dial down the aperture. It helps if the birds are flying roughly parallel to your focal plane, rather than toward or away from you. And it takes practice. These beautiful birds look amazing as they come in for a landing, too.