This may of interest to some,
Robin Hide
Bluff, L. A., J. Troscianko, A. A. S. Weir, A. Kacelnik and C. Rutz
(2010). “Tool use by wild New Caledonian crows Corvus moneduloides
at natural foraging sites." Proceedings. Biological sciences (Royal
Society) ( Epub 2010 Jan 6). 277(1686): 1377-85.
Abstract: New Caledonian crows Corvus moneduloides use tools
made from sticks or leaf stems to 'fish' woodboring beetle larvae from
their burrows in decaying wood. Previous research on this behaviour has
been confined to baited sites, leaving its ecological context and
significance virtually unexplored. To obtain detailed observations of
natural, undisturbed tool use, we deployed motion-triggered video
cameras at seven larva-fishing sites. From 1797 camera hours of
surveillance over 111 days, we recorded 317 site visits by at least 14
individual crows. Tool use was observed during 150 site visits. Our
video footage revealed notable variation in foraging success among
identifiable crows. Two nutritionally independent, immature crows spent
considerable time using tools, but were much less successful than local
adults, highlighting the potential role of individual and social
learning in the acquisition of tool-use proficiency. During systematic
surveys of larva-fishing sites, we collected 193 tools that crows had
left inserted in larva burrows. Comparing these tools with the holes in
which they were found, and with raw materials available around logs,
provides evidence for tool selectivity by New Caledonian crows under
natural conditions. Taken together, these two complementary lines of
investigation provide, to our knowledge, the first quantitative
description of larva fishing by wild crows in its full ecological
context.
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