How much does a peregrine nestling grow in a week?

Comparison of peregrine nestlings on hatch day and one week later, University of Pittsburgh nestIt’s been a week since 3 peregrine eggs hatched at the University of Pittsburgh and their parents have been feeding them frequently. 

Have the nestlings grown?  Here’s a visual comparison.

At left are two photos from the webcam, exactly the same size.  The top photo shows the chicks on the day they hatched, the bottom one shows them today. 

Indeed, they have grown.  Each chick is two or three times larger than the remaining egg and the group of chicks takes up a noticably larger portion of the picture. 

Meanwhile the unhatched egg is already a week beyond its probable hatch date.  This egg is unlikely to hatch at all, but don’t worry.  In the seven years Dorothy has nested at Pitt she always lays 4 eggs but about 40% of the time she hatches only 3 of them. 

This outcome is normal.  Eventually one of the adults will move the unhatched egg out of the way.  

At the rate the chicks are growing, they’ll need all the space they can get!

Watch the peregrines in action on the National Aviary webcam. 

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