I was lurking on seashore yesterday.
Two crane landed like 30meter from me. Shooted it on flight and another when it made spring scream.
Then slowly lowered camera and just watched what they doing ,bad place to take pictures ,lot of reeds wawing on wind.
Obviously they were totally unaware of me, watched them treating their feathers like 5min.
Raised camera slowly again looked through like 1min and changed spot autofocus, they continued what they were doing.
Then shooted like 3 fast shot,and immediately cranes raised their heads and freezed to look around.
I think shutter sound freaked them out.
Now they stalked around nervous and made usual alarm shouts and fled away couple min later.
I think silent shutter matters when shooting truelly wild birds on close ranges without blind.
Sorry about bad pics just wanted to prove they dont like shutter sound.