The observation that Galapagos finches possessed different beak shapes to obtain different foods was central to the theory of evolution by natural selection, and it has been assumed that this relationship holds true across all bird species. However, a University of Bristol-led study suggests bird beaks are not as adapted to the food types the birds feed on as it is generally believed.
In the study, University of Bristol researcher Guillermo Navalón and colleagues used computational and mathematical techniques to better understand the connection between beak shapes and functions in living birds.
By measuring beak shape in a wide range of modern bird species from museum collections and looking at information about how the beak is used by different species to eat different foods, they were able to assess the link between beak shape and feeding behavior.
“The connection between beak shapes and feeding ecology in birds was much weaker and more complex than we expected and that while there is definitely a relationship there, many species with similarly shaped beaks forage in entirely different ways and on entirely different kinds of food,” Navalón said.
“This is something that has been shown in other animal groups, but in birds this relationship was always assumed to be stronger.”
“This is, to our knowledge, the first approach to test a long-standing principle in biology: that the beak shape and function of birds is tightly linked to their feeding ecologies,” said co-author Professor Emily Rayfield, also from the University of Bristol.
“These results only made sense when you realize birds use the beak for literally everything. Therefore, also makes sense they evolved a versatile tool not just for getting food, but also to accomplish many other tasks,” added co-author Dr. Jesús Marugán-Lobón, a scientist at the Universidad Autónoma de Madrid.
The study is part of a larger research to better understand the main drivers of the evolution of the skull in birds.
“We have seen similar results before in birds of prey, but this is the first time we studied the link between beak shape and ecology across all bird groups,” said co-author Dr. Jen Bright, a researcher at the University of South Florida.
“We looked at a huge range of beak shapes and feeding ecologies: hummingbirds, eagles, parrots, puffins, flamingos, pretty much every beak you can think of.”
The team’s results appear in the journal Evolution.
Guillermo Navalón et al. The evolutionary relationship among beak shape, mechanical advantage, and feeding ecology in modern birds. Evolution, published online December 8, 2018; doi: 10.1111/evo.13655