[CT Birds] New caledonia crows

Katz1449 at aol.com Katz1449 at aol.com
Sat Oct 6 11:49:35 EDT 2007


>From Bev Propen  10/6
I thought all of you advanced birders would find this birding  news of 
interest. 
 
Clever crows are caught on camera
Rebecca Morelle
Science reporter,  BBC News

Miniature cameras have given scientists a rare glimpse into how  New 
Caledonian crows behave in the wild.
The birds are renowned for their  sophisticated tool-using ability, but 
until now, observing them in their  natural habitat has proven difficult.

But specially designed "crow-cams"  fitted to the birds' tails have shed 
light on the creatures, recording some  tool-use never seen before.

The research is reported in the journal  Science.

New Caledonian crows ( Corvus moneduloides ) are found on the  South 
Pacific island of New Caledonia.

They can use their bills to  whittle twigs and leaves into bug-grabbing 
implements; some believe their  tool-use is so advanced that it rivals that 
of some primates.
Why not  just stick a camera to a crow, hitch a ride with it, and get a 
crow's eye  view of what is going on?
Christian Rutz
But while these clever crows have  been extensively studied in captivity, 
looking at their natural behaviour in  the wild is tricky.

Christian Rutz, lead author of the paper from the  Department of Zoology at 
the University of Oxford, UK, said: "These birds  are notoriously difficult 
to study in the wild.
"They are very sensitive  to human disturbance and the terrain in New 
Caledonia is very mountainous  and forested, so it is difficult to follow 
the birds."
So the team came  up with another approach.
"Why not just stick a camera to a crow, hitch a  ride with it, and get a 
crow's-eye view of what is going on?" Dr Rutz  said.
New tools
Recent advances in mobile phone technology enabled the  researchers to 
construct a camera that was small enough to attach to a crow's  tail 
without impairing its movements.
They attached the 14g (0.5oz) units  - which also contained a radio tag to 
transmit location coordinates - to the  tail feathers of 18 New Caledonian 
crows.
The footage, broadcasted to the  researchers' custom-built receivers, 
provided the team with a unique insight  into the crows' behaviour - 
including some that had never been seen  before.
Dr Rutz told the BBC News website: "Before, we thought the crows  targeted 
their tool use at fallen dead trees where they probe for grubs; but  now we 
have observed them using tools on the ground - and that has never  been 
seen before.

"We also filmed them doing this using a new type of  tool, which was very 
surprising. We found them using grass stems - and that  is interesting 
because these stems have very different physical properties  from the 
sticks and leaves that we knew they use.

"They are using the  grass stems on the forest floor, probing the leaf 
litter, possibly fishing  for ants."
Big juicy grubs
The team is using its video footage to  investigate why New Caledonian 
crows might have evolved their tool-using  abilities. This species of crow 
is the only non-primate animal known to  create and use new tools.
Dr Rutz said: "What were the ecological  circumstances on this one 
particular island in the South Pacific that could  have fostered the 
evolution of this behaviour?"
This technology could  really change the way we study wild birds
Christian Rutz
One idea, he  said, was that the behaviour may have evolved in response to 
food  shortages.
"When we compared situations when the crows did and didn't use  tools, we 
found two pieces of supporting evidence for this," Dr Rutz  said.

"Firstly, the prey encounter rate was surprisingly small: for one  hour of 
ground foraging a crow would only pick up eight tiny morsels of food  - a 
blackbird in a garden would be taking up that many items a minute. That  
shows maybe foraging without tools is indeed challenging in this  habitat.

"Secondly, when you compare the size of the food items they get  with and 
without tools - when they don't use tools, the food items are very,  very 
small indeed compared with the food items they extract with the tools.  
This again suggests maybe they need to use tools to gain access to this  
rich hidden food resource."
The team says its video tracking technique  could be used to study other 
wild birds that are shy or live in inaccessible  habitats.
Dr Rutz added: "This technology could really change the way we  study wild 
birds."

Story from BBC NEWS:
_http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/7027923.stm_ 
(http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/7027923.stm) 
 






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