Shaping of Hooks in New Caledonian Crows
Alex A. S. Weir, Jackie Chappell, Alex Kacelnik*
Science, Volume 297, Issue of 9 Aug 2002, p. 981.
Here are some bits from that article. For us, one point is that it doesn't take a chimp brain to fashion a tool. This is not to say bird and chimp brains are equivalent. Nevertheless usually claims about chimp tool use both ignore Darwin and non-primate tool use.
We report here an experiment inspired by the observation that a captive female spontaneously bent a piece of straight wire into a hook and successfully used it to lift a bucket containing food from a vertical pipe (Fig. 1A). This occurred on the fifth trial of an experiment in which the crows had to choose between a hooked and a straight wire and only after the hooked wire had been removed by the other subject (a male). The animals had prior experience with the apparatus, but their only previous experience with pliant material was 1 hour of free manipulation with flexible pipe-cleaners a year before this experiment, and they were not familiar with wire (6).
Wire-bending behavior by a captive New Caledonian crow. This movie clip shows the seventh trial of the experiment, in which the female New Caledonian crow uses sticky tape on the side of the apparatus to bend straight wire and subsequently uses this bent wire to retrieve a bucket containing meat. At the beginning of the clip, she is already holding the straight wire in her beak, as she picked it up at the start of the trial but was immediately displaced by the male crow. Movie clips of all trials are available by request from the authors.
(You might be able to see the video again through the UNH catalog, looking up this article online.)