Washington, Oct 5 : Scientists have discovered that the wild New Caledonian crows use a greater variety of tools and foraging techniques than previously thought.

Previous research on captive birds has demonstrated the species' remarkable cognitive and tool-making abilities. Field studies of remnants left by tool-making birds – such as leaves that had been bitten into strips to serve as probes – has also suggested that tool use is common in wild populations.

Now, a research team led by Christian Rutz of the University of Oxford in England has had the first few direct observations of crows making and using tools in a natural setting.

The species live in the mountainous forests on islands in the South Pacific and are highly sensitive to disturbance by human observers.

As part of their study, Rutz and his team fastened 13-gram (0.5-ounce) cameras – slightly heavier than two U.S. quarters – on the tail feathers of individual crows.

“The lens is pushed forward through the central tail feathers and peeks through the bird's legs. You have a shot showing part of the crow's belly and whatever appears in front of the bird,” said Rutz.

He said although their pilot study was intended primarily as a demonstration of the new technology, they gained important new information about the crows' life in the wild.

“With seven hours of video [from 12 individual crows] we made more new discoveries than in hundreds of hours of field observations,” Rutz said.

He said researchers already knew that the crows “fished” for beetle larvae in dead wood with tools made from sticks or leaves. But, the new video footage showed that the crows also foraged extensively on the ground, using a previously unreported type of tool – stalks of grass – to turn over loose material in search of insects.

“The fact that they use tools on the ground shows that the niche they exploit with their tool use is much larger than previously thought,” said Rutz.

Rutz said another discovery was that the crows did not always use whatever stick or stem was close by to serve as a foraging tool, but that they carried a favoured tool in flight from one location to another.

Rutz and his colleagues describe their bird-mounted video cameras in this week's edition of the journal Science, reports the National Geographic. (ANI)