The earliest bird got the worm: new study finds a 120-million-year-old group of birds probably ate insects rather than fish

As the saying goes: "The early bird gets the worm", and a new study from Hong Kong suggests a group of birds from 120 million years ago may have, in fact, eaten worms. Or, more precisely, invertebrates.

Published in the peer-reviewed journal BMC Biology this month, the study is important because it creates a framework for scientists to learn how modern birds became ubiquitous in today's ecosystems.

The scientists analysed a genus of prehistoric birds called Longipteryx and, by comparing the fossils to modern birds, gathered enough evidence to pinpoint that the animals probably ate invertebrates or were "generalists", meaning they ate a bit of everything.

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"Today, we have about 11,000 species of birds, and they live almost everywhere on the planet in almost any environment you could imagine," said Michael Pittman, a palaeontologist at the Chinese University of Hong Kong and an author of the study. "But actually understanding where that comes from is not very well-known."

"We wanted to use as many lines of evidence as we can to reconstruct what early birds were eating," he said.

Before the study, scientists had assumed Longipteryx ate fish because they had teeth, which modern birds do not.

However, by studying the animal's jaw movements and strength, body mass and claw design, the team concluded that it would be unlikely that the Longipteryx diets involved fish.

"Diet is very difficult to determine for any extinct animal; it has taken decades of studies to determine diet in other dinosaur groups, and diet is still controversial for some," said Case Vincent Miller, a PhD candidate at the University of Hong Kong and lead author of the study.

"I suspect the reason bird diet studies are so far behind is that China's rich bird fossil resources have been understudied for a long time."

Vincent Miller added that the analysis leans towards the Longipteryx being an insect-eater because of traits it shares with modern bug-eating birds. But, because modern birds eat almost anything, a generalist diet could not be ruled out.

The team chose the Longipteryx because it is a diverse group of extinct birds and their fossils are well-preserved.

One of the insightful parts of the study is the team's findings which give us a snapshot into regional ecosystems from the Cretaceous period from about 145 to 66 million years ago. Because birds are so ubiquitous, scientists can learn a lot about an ecosystem just by analysing them.

The new study enlightened the scientists that these ancient birds probably lived lower in the food chain than many birds do today. There is no evidence that points to some birds eating other birds like owls and hawks do today.

"Coming into this study, people were saying [prehistoric] birds were focused on the lower levels of the food pyramid," said Pittman. "At the moment, what we are seeing is confirming what we know so far."

Part of why the diet took so long to analyse is because the team first had to compare and contrast the diets of modern birds and figure out what traits could be applied and studied in fossils.

For example, claws from apex predator birds like eagles look a lot different from birds lower in the food chain, meaning fossilised claws could tell us more about what the bird ate.

"It was a mammoth task," said Pittman. "It took years of effort to get to this point."

Pittman and Vincent Miller were particularly excited about how the team's process could be applied to other ancient fossils by scientists. The "multiple-line approach" could be applied to mammals to help us learn more about what the earliest animals ate.

Vincent Miller said: "One could apply our framework to groups other than birds, but this should be done with caution as it was designed with birds in mind. For instance, body mass is a strong indicator of diet in birds, but snake body mass says little about their diet."

Pittman said: "We have put ourselves in a great trajectory for modern birds, and we hope to have a detailed idea of what is going on and answer that question of how the modern ecology arose."

"We hope to inspire other palaeontologists and see this approach applied to other groups, which to me is very exciting."

This article originally appeared on the South China Morning Post (SCMP).

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