Pretty much.
I had one take a great disliking to my hat one day, he seemed ot think my hat was a rival bird.
If I came close to his nest space with the hat on, the bird flipped out and circled my head making that 'chack chack' sound.
If I went by without the hat, he ignored me.
Sent the odlest of the three of us past with the hat on, and the bird flipped out.
So it was definitely the hat.