The New Caledonian crow has a weird beak, but it's there for a reason. Researchers in Ithaca, N.Y., have taken a closer look at this large bill and found that it evolved with the use of tools.
"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,'" crow expert Kevin McGowan of the Cornell Lab of Ornithology said. "Their bill is shorter than a regular crow's It's blunter, and it doesn't curve down like nearly all bird bills do."
In order to find out what this bill might be used for, the researchers used shape analysis and computer tomography scanning to compare the shape and structure of the crow's beak with its crow relatives. They also compared it to a woodpecker species with a similar foraging niche.
"This study shows that the unique bill contributes to the birds' ability to use and probably make tools," McGowan 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."
These tools include everything from sticks to barbed leaves or hook twigs, which are used to get food from the trunks of trees. The crows poke grubs until the grubs become annoyed and latch onto the tool to bite it. The crows then remove the grubs from the trees to eat.
It's likely that birds with blunter, straighter beaks were more easily able to handle tools, McGowan said. Over time, these features evolved. In the New Caledonian crow, the lower mandible curves slightly up, which probably gives the crow more strength to use the tool. In addition, the straight beak allows the crow to actually see what it's doing since it's within the bird's binocular vision.
"They hold the stick tool so it goes up along the side of their head along the length of the bill," McGowan said. "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 findings reveal a bit more about these crows and how their beaks are key to their tool use.
The study was published in the March 9 issue of the journal Scientific Reports.
