Diet might not have influenced the shape of the avian skull, after all, new research led by the University College London and the Natural History Museum has discovered.
In a recently published paper, the researchers challenged Charles Darwin's 19th-century observations of finches in the Galápagos Islands, where Darwin concluded that how a bird forages and eats heavily influenced the shape of its skull. However, the new research analyzed more bird species and found that shared ancestry and behavior are more important to their evolution.
Evolution Of Bird Skull
"If we apply Darwin's conclusion for different kinds of birds who primarily eat fish, pelicans and penguins should have exactly the same head and beak shape, as they both use their beaks to eat fish," Ryan Felice of University College London Biosciences, one of the authors of the study, stated. "However, pelicans have a long beak and large throat pouch, while penguins' beaks are comparatively small."
Dr. Felice explained that penguins and pelicans have different ways of acquiring their food that became apparent in the evolution of their skulls. Pelicans catch fish by trapping it in their pouches then tipping back to drain the water and swallow their meal immediately. Meanwhile, penguins have a series of spines in their mouths to their throats so that fish does not escape.
"If you are descended from a duck-like ancestor, you will probably have a duck bill, no matter what diet you have," he stated. "However, shared diet establishes the parameters of skull evolution, determining the range of potential shapes which can evolve."
Diet Linked To Rate Of Cranial Evolution
The study, however, also found that birds that survive on a diet of grains and nectars have the highest rate of cranial evolution. Meanwhile, terrestrial carnivores exhibited a slower rate of cranial evolution.
According to Anjali Goswami of the Natural History Museum, this can be attributed to natural selection. Birds that feed on seeds and nectar such as finches, quails, and hummingbirds have more competition and, therefore, must evolve to continue surviving.
While their study focused on skulls, the researchers say that their findings might also be true for the evolutionary changes of parts of the body involved in catching and digesting prey.
The study published in The Proceedings of the Royal Society looked at the skull of 352 bird species, which represent 159 out of the total 195 families that exist today. According to the researchers, this is the biggest study of its kind.