The Mother Troodon, heavy with eggs, moved slowly between the nest mounds of the Maiasaura duckbills. She peered over the rim of one while the parent’s back was turned.

She saw fuzzy-feathered young poking their heads out of the shells they’d just pecked open with their beaks. No eggs were unhatched, she saw. Not a place to leave her eggs.

On she went in the twilight, silently peering into nest after nest, avoiding the gaze of the watchful duckbill parents all the while. At last she came upon a neat spiral of nearly 20 eggs – none of them hatched, and no nestlings to be seen.

She climbed silently into the nest and slid down in the middle of the nest. She crouched lightly over the large white eggs and slowly squeezed out egg after egg. Hers were not big and rounded like the Maiasaura’s eggs. Troodon eggs were long and narrow, more blue than white.

For a long hour the Troodon laid eight of her eggs, each one nestled between two of the duckbill’s eggs. Beside her she could hear the loud chewing of the Maiasaura as she ground plants in her flexible jaws to make a warm blanket of plant bits to lay over the eggs.

The Maiasaura turned. Was that a shadow she saw in her nest? She bellowed and charged toward the dim shape in the twilight.

The mother Troodon saw the huge dinosaur coming fast at her. She pulled herself up and out of the nest with the her long sharp hand claws, and slide down the outer slope, out of sight.

The Maiasaur stared out into the night. She saw only the outlines of other duckbills and their nests. She heard only the squawks of hungry hatchlings from nests near and far.

She looked down at her nest and saw only eggs – some small, some large, but all hers she thought. She opened her jaws wide and spat out a great wad of chewed branches and leaves. Gently, she spread the soggy mess over the eggs – Troodon and Maiasaura eggs alike.

The mother Troodon looked back one last time before rushing off to rejoin her family. Guarded by the immense duckbills, her babies would be safer than she could keep them from nest-raiders – the dromaeosaur raptors. The raptors were bigger and stronger than any Troodon, but no match for an angry mother Maiasaura.

Her babies could hatch safely. But for how long could they stay safe?