Just Keep Waiting, Just Keep Waiting, Waiting, Waiting.....

This is as bad a waiting on Christmas....waiting, watching, waiting, watching.
Hopefully within the next week and half, we will start to see a change in Durand and Spark's behavior to indicate that a hatch will occur soon. 
A day or so prior to hatching the chicks will begin vocalizing and pecking from inside the eggs.  The adults can hear the chirping and feel the vibrations, this causes their behavior to change.  The adults may appear restless, getting up and looking down at the eggs, settling back down, then getting up again a short time later. 

Based on when the last egg was laid we estimate hatching could start around Saturday April 27th.  Just like with gestation in humans, incubation in birds is not an exact science.  Don't be surprised if  hatching begins a day or so early and please don't panic if the hatch starts a little later.

On an unrelated note, a viewer asked a question about the white covering that comes over the falcon's eyes when it goes to sleep.  This is most likely just the birds eyelid.  But most animals have a nicitiating membrane that protects their eyes (fish, amphibians, reptiles, birds and mammals have this feature, it's rare in primates).  The nictitating membrane is a transparent or translucent third eyelid that is drawn across the eye for protection and to moisten the eye while maintaining visibility.  In birds of prey this membrane helps to protect the parents' eyes from hungry chicks while feeding them.  The nicitiating membrane is particularly useful for peregrine falcons when they are in a 200 mile/hour dive.  Blinking their third eyelid repeatedly clears away debris and moistens their eyes in flight.
Thanks for the great question.