I agree. They can somehow sense us.Well, as no one really knows for sure I am going to assume they get to the point that they know foods coming,
My avic is a calm sweetheart with me always , but a total spaz if anyone else opens her enclosure, so they may not know us per say or even like us, but I do believe they get accustomed to us and relax a bit.
(other then my tiny P cambridgei sling who threat poses me constantly)