Birds are very intelligent so I think they know that the food was a little past its prime, why the two were placed at the same time so one was consumed first before the other, so these birds follow each other if one tasted the food from the first and then went to eat from the other container it must not have found it the same, so other birds observed that she left and so made the decision to follow her.

I really don't know much about this haha so I'm just saying what I think, I thank you for seeing my post.