For bird photography especially there are two schools of thought for camera settings, being all-to-mostly AUTO, and mainly Manual.
I grew up with all manual as there wasn't any Auto to speak of, and most Auto settings were quite crude by today's standards. Bird photography, and BIF in particular is quite challenging as there are so many things going on, causing endless variables.
For my particular circumstances using a Canon T2i (light, competent) and Canon 400L (light, tack-sharp wide open) I normally reduce the variables by shooting aperture priority, f5.6 (wide open) and take whatever shutter speed I get. I usually use Auto-ISO capped at 1600. But sometimes, as with this image, the ISO auto-'selected' causes too low a shutter speed, for my liking. I prefer closer to 1/1000 for birds, if possible.
I sometimes manually set the ISO at 800, sometimes use Auto-ISO (capped at 1600). I don't sit in blinds or use a tripod/support so my variables are always changing so I try to second-guess my options.
Sometimes with great success, sometimes not. But that''s the case with any camera, lens, support and situation.
