The last thing I needed to see to be sure the Fifth Avenue nest had hatched I saw on Monday evening, the classic feeding of an eyass.  The mother pulls a piece of food off the prey and gently twists her head by 45-90 degrees to hand the food off to the eyass.  Seeing this behavior removed all doubts about the nest hatching for me.  Now the questions is how many eyasses is she feeding, two or three?