Modern birds are consideration to have evolved from theropods, a group of carnivorous dinosaurs that include such identifiable predators as the Velociraptor and Tyrannosaurus rex.
In study published in the journal Science in 2009, scientists examined the way existing birds nurture their eggs, claiming that only male theropods took part in incubation. But the study, which compared the size of male and female birds with the size and number of eggs that were laid, omits some important factors, said Geoff Birchard, a professor in the department of environmental science and policy at George Mason University in Fairfax, Va., and co-author of the new study.
"They looked at the number of eggs and how big they were, and said they could figure out whether mommy incubated, daddy incubated, or both did," Birchard told LiveScience."The problem is, the biology following it is a little bit off."
Birchard and his colleagues frequent the 2009 study using more data from living bird species. They resolute that comparing the size of the birds with the grab size - which is determined by multiplying the number of eggs lay in a nest by the volume or mass of the eggs - could not successfully establish whether it was the male or female guarding the eggs.
"Our psychoanalysis of the relationship between female body mass and clutch mass was motivating in its own right, but also showed that it was not achievable to terminate anything about incubation in extinct distant relatives of the birds," study co-author Charles Deeming, a researcher at the University of Lincoln in the United Kingdom, said in a declaration.
Part of the problem is that birds do not all exhibit the same threatening behavior.
"There's a huge amount of difference with birds," Birchard said."With certain bird types, two parents are always involved, but with some bigger birds, only the daddy is incubating the eggs. With dinosaurs, overall, there's a huge amount of variety, too."
And whether the actions of modern birds can be used to forecast the behavior of dinosaurs is also a source of argue.
"There are great differences of opinion about it," Birchard said."There's a long time gap between dinosaurs and the origin of birds, so it's an awful long time for us to say what's being done with birds was also being done with dinosaurs. We use this kind of inference sometimes, but birds are also a very exceptional group."