Unique beak evolved with tool use in New Caledonian crow

March 15, 2016
A 3-D reconstruction of the New Caledonian Crow skull with key measuring points. Credit: Matsui et al. (2016)

It was as plain as the beak on a bird's face. Cornell ornithologist and crow expert Kevin McGowan recalls the day in the late 1990s when he first saw stuffed specimens of the New Caledonian crow.

"I remember saying to a student, 'I don't know what this bird does, but it does something different from any other corvid on Earth because its bill is so weird,'" said McGowan, project manager for distance learning in bird biology at the Cornell Lab of Ornithology.

In 2000, McGowan read a paper by Gavin Hunt, a senior research fellow at the University of Auckland, New Zealand, on use by these crows and he had an insight into the New Caledonian crow's unusual beak.

Now, Hunt, McGowan and a team of scientists from Japan have quantified what makes the New Caledonian crow's beak different and how it got that way. Their findings were published March 9, 2016 in the journal Scientific Reports.

"We used shape analysis and CT [computer tomography] scanning to compare the shape and structure of the New Caledonian crow's bill with some of its crow relatives and a woodpecker species with a similar foraging niche," said lead author Hunt.

"This study shows that the unique bill contributes to the birds' ability to use and probably make tools," he said. "We argue that the beak became specialized for tool manipulation once the birds began using tools, and that this enhanced tool manipulation ability may have allowed the crows to make more complex tools."

Such tools may range from sticks to barbed leaves or hooked twigs used to fish the crow's favorite food from the trunk of a tree - the juicy grubs of the longhorn beetle. The birds annoy their prey by poking around the grub's large, sensitive mandibles. When the grub grabs the stick or other tool, the bird hauls it out.

"Their bill is shorter than a regular crow's," McGowan said. "It's blunter, and it doesn't curve down like nearly all bird bills do. The lower mandible actually curves slightly up, which likely gives it the strength it needs to hold the tool. And because the bill doesn't curve downward it brings the tool into the narrow range of the bird's binocular vision so it can better see what it is doing."

Birds with blunter, straighter bills were probably more adept at handling tools for foraging and over time those features evolved, McGowan said. Tool use has now become ingrained in the crow's biology. In the case of the New Caledonian crow's beak, you might say it's not so much "you are what you eat," but "you are how you eat."

"They hold the stick tool so that it goes up along the side of their head along the length of the bill," McGowan explains. "Apparently there are birds that favor one side of the head over the other—left-sticked or right-sticked, you could call it—it's really cool."

The question that cannot be answered is why the started using tools in the first place. It may have been a matter of chance because most do just fine foraging with their beaks and feet without resorting to tool-making, McGowan said.

Explore further: Why clever crow is no bird brain

Related Stories

Why clever crow is no bird brain

October 9, 2012

Biologists on Tuesday said they had figured out how the New Caledonian crow, a bird famed for using tools, does its party trick.

Crows caught on camera fashioning special hook tools

December 22, 2015

Dr Jolyon Troscianko, from the University of Exeter, and Dr Christian Rutz, from the University of St Andrews, have captured first video recordings documenting how these tropical corvids fashion these particularly complex ...

Why tool-wielding crows are left- or right-beaked

December 4, 2014

New Caledonian crows—well known for their impressive stick-wielding abilities—show preferences when it comes to holding their tools on the left or the right sides of their beaks, in much the same way that people are left- ...

New Caledonian crows show strong evidence of social learning

August 26, 2015

Among our greatest achievements as humans, some might say, is our cumulative technological culture—the tool-using acumen that is passed from one generation to the next. As the implements we use on a daily basis are modified ...

Crows, like humans, store their tools when not in use

May 21, 2015

Researchers at the University of St Andrews have discovered that crows, like humans, store their tools when they don't need them. The study published today in the Proceedings of the Royal Society B is the first to examine ...

Recommended for you

Ten months in the air without landing

October 27, 2016

Common swifts are known for their impressive aerial abilities, capturing food and nest material while in flight. Now, by attaching data loggers to the birds, researchers reporting in the Cell Press journal Current Biology ...

Study shows mixed fortunes for Signy penguins

October 27, 2016

A forty year study on a remote Antarctic island shows that while populations of two penguin species are declining, a third is increasing. Analysis of census data from Signy Island in the South Orkney Islands reveals that, ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.