May 29th

What Nests Tell Us

A nest is an intimate thing. It’s not a home, but a place only for birth and nurturing. The first publicly heralded discovery of dinosaur eggs took place in Mongolia in 1923. Since then, paleontologists have discovered and described dinosaurs nests all over the world. These relics from the distant past shed light on how life began in the Mesozoic.

Citipati brooding its nest / AMNH

In the 1970s, dinosaur nesting colonies were discovered in Montana–giving scientists clues about the parenting skills of dinosaurs. Eggshells were found crushed in the nest, and the associated remains of youngsters showed that their bones hadn’t developed enough for walking. This means that the adults were bringing food back to the nest until the young were large enough to walk out on their own. Other species exhibited largely intact eggshells, meaning that the baby dinosaurs were up and out of the nest quickly and foraging alongside their parents.

We also find that dinosaur colonies resemble bird nest sites, in that the spacing between the nests is equal to the length of an adult. So the dinosaurs were closely packed together, as avian colonies are today. Unlike birds, the big dinosaurs were too heavy to sit on their eggs. They’d crush the little things, rather than incubate them. Dinosaurs relied on rotting vegetation to provide the necessary heat. Smaller dinosaurs, like Citipati (pictured above) were able to incubate their eggs in a more typically avian fashion.

Dinosaurs are often regarded as large animals, but their eggs don’t get very big. The eggshell needed to be thin enough for the baby’s respiration to occur, while also being thick enough to hold the egg together. This means that even the largest dinosaurs began life in small eggs, and by studying the bones of youngsters, we can see how fast they grew–and in many cases, their growth rates were astronomical, reaching adult size in just a few years.

In less than a century, we’ve learned so much from dinosaur nest sites. Share your favorite dinosaur egg photos and memories with us on Facebook and Twitter using the hashtag #TDIDinos.