Tool use is extremely rare in the animal kingdom. According to estimates, the behavior has been documented in less than one percent of all known genera, and in an even smaller percentage of species.
Among the few birds that use tools is New Caledonian Crow, which can be found only on a Pacific archipelago located 750 miles east of Australia. For 20 years, scientists have considered the species the sole member of the crow family to possess the ability.
But now, according to a paper published recently in the journal Nature, we know that it’s not alone. The critically endangered Hawaiian Crow, or ‘Alala, also uses tools.
The species has been extinct in the wild since the early 2000s. Only 131 of the birds remain, all of which are kept in facilities operated by San Diego Zoo Global on Maui and the Big Island of Hawaii, where the crows are being bred for release.
“We had previously noticed that New Caledonian Crows have unusually straight bills, and wondered whether this may be an adaptation for holding tools, similar to humans’ opposable thumb,” says lead author Christian Rutz, of the University of St. Andrews, in Scotland.
By searching for the characteristic among other corvids, Rutz quickly homed in on the ‘Alala.
He and his team tested 104 of the 109 Hawaiian Crows alive at the time and found that 78 percent used tools spontaneously to probe for food tucked in horizontal and vertical holes and crevices in a wooden log.
“Using tools comes naturally to ‘Alala,” says Rutz. “These birds had no specific training prior to our study, yet most of them were incredibly skilled at handling stick tools and even swiftly extracted bait from demanding tasks.”
The crows frequently shortened or made other modifications to their tools, and the researchers report that a number of the birds manufactured tools from plant materials.
A version of this article appeared in the December 2016 issue of BirdWatching.
Read the paper
Christian Rutz, Barbara C. Klump, Lisa Komarczyk, Rosanna Leighton, Joshua Kramer, Saskia Wischnewski, Shoko Sugasawa, Michael B. Morrissey, Richard James, James J.H. St Clair, Richard A. Switzer, and Bryce M. Masuda (2016). Discovery of species-wide tool use in the Hawaiian crow Nature, 537, 403-407.
Read about the ‘Alala program of the San Diego Zoo Institute for Conservation Research.
Hawaii’s new forest trail lets birders discover the endangered Palila.
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