Scientists have found that a small, bird-like North American dinosaur incubated its eggs similarly to brooding birds, according to a new study that may bolster the evolutionary link between birds and dinosaurs.

In a bid to better understand whether dinosaurs completely buried their eggs in nesting materials like crocodiles, or if they left them partially uncovered like brooding birds, researchers at the University of Calgary and Montana State University closely examined the shells of fossil eggs from a small meat-eating dinosaur called Troodon.

This specific dinosaur species, which was known to lay its eggs almost vertically, would have only buried the egg bottoms in mud, they reported in Paleobiology journal on Thursday.

"Based on our calculations, the eggshells of Troodon were very similar to those of brooding birds, which tells us that this dinosaur did not completely bury its eggs in nesting materials like crocodiles do," said study author Darla Zelenitsky, assistant professor of geoscience at the University of Calgary.

Paleontologists have always struggled to answer the question of how dinosaurs incubated their eggs, because of the scarcity of evidence for incubation behaviors.

As dinosaurs' closest living relatives, crocodiles and birds offer some insights.

Scientists know that crocodiles and birds that completely bury their eggs for hatching have eggs with many pores or holes in the eggshell, to allow for respiration.

This is unlike brooding birds which do not bury their eggs; consequently, their eggs have far fewer pores.

The researchers counted and measured the pores in the shells of Troodon eggs to assess how water vapor would have been conducted through the shell compared with eggs from contemporary crocodiles and birds.

They are optimistic their methods can be applied to other dinosaur species' fossil eggs to show how they may have been incubated.

"For now, this particular study helps substantiate that some bird-like nesting behaviors evolved in meat-eating dinosaurs prior to the origin of birds. It also adds to the growing body of evidence that shows a close evolutionary relationship between birds and dinosaurs," Zelenitsky said.