Name: Kurt Woodbridge , Va (Zone 7a) Jai guru deva om
looks like a wren egg , you can try to put it back , maybe a predator knocked it out or a brown headed cowbird replaced it with one of her own eggs.
either way the parents may abandon the nest
A pint can't hold a quart , If it is holding a pint it is doing the best that it can.
and it is written ,
if the evil spirit arms the tiger with claws , brahman provided wings for the dove.