Haha...those sifus very skill in camo and sheath so that the bird would not detect them.
Focal length also important.
The birds are better in camo themself,that's why we always hear the calls but can't see the birds.
Most of the time the birds will see u before u see them,unless u use a hide and wait for them to come.
But some birds are so skittish that when they see a hide,they will not perch nearby..they are smart creatures.
my recent attempt on one of a skittish bird that hide doesn't help..I had to hide behind the bushes and about 15-20m away from its usual perch.
For starters,i would say go out and find the birds to shoot first rather than wait..its easier to shoot the bigger birds first like Egret and Herons or common birds like Sunbirds,Oriole...etc