Bird lovers help researchers uncover secrets of beak evolution

A team of researchers led by the University of Sheffield asked the public to help measure beak shapes from more than 2,000 bird species. These were 3D-scanned from specimens at the Natural History Museum as well as the Manchester Museum.

The study, published in the journal Nature, sheds light on the speed and patterns of bird evolution.

Findings

Birds have a startling array of beaks with many functions, from nest building and preening to feeding and self-defence.

Thanks to the data provided by citizen scientists, the researchers were able show that the diversity of bird beaks expanded early in the group's evolutionary history, around the time other dinosaurs died out.

The team found that the most unusual beak shapes often emerged over relatively short periods and therefore involved exceptionally fast evolutionary change. 

The burst of changes that occurred 80 to 50 million years ago enabled birds to exploit a wide variety of habitats and food sources in a rapidly changing world.

Changes to bird beaks then became much smaller over time as birds filled ever-narrower ecological niches.

So the vast range of basic shapes was generated early on, while later evolution fine-tuned them.

According to lead author Dr Gavin Thomas, an evolutionary biologist from the University of Sheffield, 'The shape of a bird's beak is an important indicator of the food it eats and the way it forages.

'This project has given us key insight into how evolutionary processes play out over millions of years - with major bursts of evolution as new groups emerge, and more fine-scale changes thereafter.'

The advantage of museum specimens

Measuring animals in the wild to prepare 3D models would have been almost impossible, but bird skins housed in natural history collections are ideal. They provide relatively quick and easy access to a large range of species.

The Natural History Museum's bird skin collection, housed at Tring, has almost 750,000 specimens and represents about 95% of the world's bird species.

'This project would not be possible without museum collections,' says Mark Adams, Senior Curator of Birds at the Museum. 'The Museum's bird collections are one of the largest and most comprehensive of any museum in the world, and so pivotal to this project.'

Traditionally, bird beak measurements tell us about the size of a beak, but provide little information about the shape - missing important characteristics such as curvature and hooks. These attributes are important when considering how and why bills have diversified.

Scanning bird beaks in 3D made it possible to capture and analyse such information.

This video shows how specimens were scanned at the Museum at Tring (there is no audio):

How citizen scientists helped

To help with the study, members of the public accessed the 3D models of the beaks through the Mark My Bird crowdsourcing website. They highlighted specific features common to all specimens, such as the tip and midline, and traced along the side edges. The process was repeated by multiple individuals for accuracy.

This process, called landmarking, quantified the beak shape, turning it into data that could be analysed. Scientists were then able to compare and contrast the beaks of different species.

By combining the information from DNA-based evolutionary trees, the research team were able to infer ancestral beak shapes as well as rates and patterns of beak evolution stretching back more than 100 million years.

The collected beak shape data will soon be added to the Museum's Data Portal so that scientists, researchers and the public can access it in the future.

'With the efforts of volunteers from across the world, the study has provided a unique new data set for the study of bird ecology and evolution,' concludes Dr Thomas.

'There are many questions that could be tackled with the data, including many our team have not yet thought of.'