Charles Darwin's observations of the 19th century on the Galapagos Islands led to the conclusion that the formation of birds was influenced mainly by the ecosystem; as the bird spoils and eats, forms the shape of the skull and evolutionary changes.
However, a new study by UCL and NHM researchers, which examines a wider range of species than ever before, has shown that on a global scale, common origin and behavior are more important factors than diet.
A study published in the Journal of the Royal Society Proceedings B examined the shape of the skull of 352 species of birds representing 159 of the 195 existing families, making it the largest study
. "If we apply the conclusion of Darwin to different species of birds , which primarily eats fish, pelicans and penguins should have the same shape of head and beak, as both use their beaks to eat fish, a long beak and a large throat pouch, while the penguin beak is relatively small, – explained Dr. Ryan Felice (UCL Bi osciences), one of the authors of the study.
"Although they eat the same thing, pelicans and penguins acquire their booty in different ways, demonstrating the important role played by the behavior in the evolution of the skull.
Root penguins have a number of thorns directed down their throats, so that food stays there when they are caught. Pelicans ingeniously catch fish in a sac, and then lean it back to drain water and swallow fish immediately.
"Evolutionary history, and not a diet, most affected the shape of the skull. As a duck ancestor, you probably have a duck bill, no matter what diet you have. However, a common diet sets the parameters of the skull's evolution, defining a range of potential forms that can develop, – added Dr. Felice. Researchers also found that birds that eat corn such as finches and quail, as well as those who survive on a nectar of flowers, like hummingbirds, show the highest rate of evolution of the skull. In contrast, terrestrial predators – hawks, falcons, owls and other birds that hunt and eat using their claws – show a very slow rate of change in the skull.
"Natural selection works here," said Professor Anzali Goswami, Research Director at the Museum of Natural History and co-author of the study
. "Birds that eat nectar or seeds will experience great competition for resources and must develop to survive."
The research focuses on the skull, but we assume that other parts of the body can be formed by diet and ecology, such as wings, claws and stomachs, because they are those parts of their bodies that are crucial for catching and digging prey.
The research used modern equipment for the construction of 3-D digital high-resolution skull models. This allowed the researchers to build much more points on the skull than before, which allowed them to make reliable and accurate measurements.
"The next step is to extend this analysis to other animal groups, such as mammals, reptiles and dinosaurs," said Dr. Felice. "Our goal is to understand all the various factors that have shaped the evolution of the skull over time."  Dr. Felice's partners at work were Dr. Imperial College London, Dr. Alex Pythot (UCL Biosciences) and Professor UCL Biosciences & Natural History Museum.
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Dietary niche and the evolution of cranial morphology in birds, Proceedings of the Royal Society B: Biological Sciences (2019). DOI: 10.1098 / rspb.2018.2677