My theory,, you were standing still and not making any noise...A duck or goose in flight with several others is hearing many things. Its hearing the wind, its hearing wing beats, its hearing the birds its flying with making calls.. It only hears a part of the sounds you make,, doesnt have to be perfect,, it tries and locates those sounds..

Does calling verses no calling make a difference.. sure does! I hunted a very heavily hunted public area this year. I got there at 10am.. There are 4 blinds within eyesight all had hunters in them. I got there and heard the other guys calling and sat down with my buddies. No one out there could call worth a poop,, and a couple blinds werent callingat all. I got there and from 10am till 2 pm I called in limits for everyone in that blind! Not one quality shot was fired out of those other blinds. The difference,, someone that could call ducks a little better than the 3-4 time a year duckhunter!