No, this isn’t the Museum’s famed avocado specimen—below, you see the large, thick-shelled, and emerald-hued egg of the Northern Cassowary.
Visitors can see examples like this—among other amazing ova—in the special exhibition Dinosaurs Among Us.
There, you’ll get a look at how ancient dinosaurs never went extinct. Instead, they gave rise to the first birds, some of which abandoned flight for the terrestrial lifestyle pursued by species like cassowaries.
This egg’s green tint is actually a clue to where—and how—the cassowaries nest, and as you may have guessed, it’s not up a tree. Like their closest relatives, the emus, these ground-dwelling birds build nests among thick foliage, scratching shallow depressions in the dirt and lining them with leaves and grass.
These well-camouflaged nests usually hold between three and six eggs, which are watched over by the male. The proud papa incubates them for nearly two months while the female departs, sometimes to mate again. Once the eggs hatch, the father also cares for the young birds for nine months or longer, helping the chicks find food and protecting them from predators.
Thanks to a few extraordinary fossils, paleontologists now think that this nesting behavior looks very similar to that of some dinosaurs. A cast of one such specimen, Citipati osmolskae, is featured in Dinosaurs Among Us, along with fleshed-out models. Discovered in 1993, this oviraptorid dinosaur specimen is positioned over the center of a large nest, assuming a protective posture over its eggs that is similar to that adopted by modern birds like hawks.
Uncovered at Ukhaa Tolgod, Mongolia, by scientists from the Museum and the Mongolian Academy of Sciences, the original Citipati fossil shows that nesting was present more than 80 million years ago, far back in the dinosaur line. Paleontologists think that behaviors like parental care by males may have already developed by that time, too.