Ahhh that makes a lot of sense and yes I have noticed the others look up too plus my drakes do their call and my head duck hen quacks. I like that you told me they make a noise b'cos its harder for a predator to attack when they know they've been seen.
Had a strange experience the other day though, my mum came by to help by giving me a lift to dump some rubbish down at our local tip, I got her to park up around the back of the bungalow so I could load up her car via the back gate, I nipped indoors to get something and I became aware that both flocks were completely silent, so I took a look out of the window and saw all 8 huddled together in a corner, I went out to find my mum standing by the back door, she had decided to come in and see them and stood still when she realised her presence was frightening them. Even though I was there they still didn't come out and just kept giving her the side eye, I told her to wait in the car b'cos her being there was scaring them so much. They have never before behaved like this, usually they are extremely vocal and often will rush at an intruder and if the intruder doesn't go they'll attack, especially Pedro, she's like a guard dog! I used to worry about the neighbourhood cats attacking my birds but after encountering my birds, none dare come in my garden at all anymore. If we have a visitor who wants to come meet them we always make sure one of us go out first, I just don't recognise nor understand their behaviour on seeing my mum, they just are never quiet, especially when scared they make even more noise. Thing is, she met them back August and they didn't react that way then, in fact they barely took any notice of her. Strange one that.