Washington - Mounting tiny video cameras to the tail feathers of crows, researchers discovered that the birds use a variety of tools to seek food, and even make their own tools, plucking, smoothing and bending twigs and grass stems.
"We observed a new mode of tool use that was not known before. We saw them use tools on the ground, using a little grass stem to poke and fish into nests," researcher Christian Rutz of England's University of Oxford said.
New Caledonian crows had been known to use sticks to probe rotting trees for grubs, but they were never seen to use tools on the ground before.
So they came up with the idea of feather-cam, a 13-gram video camera they tested on lab crows and then took to the forest. The camera is attached to the tail feathers of the crow and bends forward to record the belly, feet and sometimes the head of the bird.
"They do make tools, which is quite unusual. They do not just pick up any random twig," Rutz said.
He said the birds select the twig they want, break it off and sometimes smooth it or bend it into a hook. They also like to use dry grass stems, which are more flexible, he explained. Especially good tools were kept for future use.
The crows were observed to eat an average of eight small items per hour, such as beetle larvae, small lizards and small fruits.
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