New Caledonian crow
New Caledonian crow | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Family: | Corvidae |
Genus: | Corvus |
Species: | C. moneduloides
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Binomial name | |
Corvus moneduloides Lesson , 1831 | |
The New Caledonian crow (Corvus moneduloides) is a medium-sized member of the family
Description
The New Caledonian crow is a moderate-sized crow (40 centimetres (16 in) in length), similar in size to the house crow, but less slender-looking. The bird has an all-black appearance with a rich gloss to its feathers of purple, dark blue and some green in good light. The beak, feet and legs are all black. The beak is moderate in size but is unusual in that the tip of the lower mandible is angled upwards, making it somewhat chisel-like in profile. It has been suggested that this beak morphology evolved due to the selective pressure of needing to hold a tool straight.[6]
The vocalization is described as a soft "waa-waa" or "wak-wak", and sometimes as a hoarse "qua-qua" or "waaaark". Across New Caledonia, the bird is often referred to as a 'qua-qua' due to its distinctive call.
Distribution and habitat
The bird is endemic to the islands of
Ecology and behavior
The New Caledonian crow eats a wide range of food, including many types of
This species is known for using plant material to create stick and leaf tools to capture prey hiding in cracks and crevices. These tools can have naturally occurring barbs, or are sometimes fashioned into hooks by the birds. The tool is inserted into the crack or crevice in the log or branch, and the prey is agitated into biting the tool. The crow then withdraws the tool with prey still attached, and devours the prey. Grubs caught in this way have been shown to be an integral part of the crows' diet.[7] The New Caledonian crow appears to fill the ecological niche of the woodpeckers and the woodpecker finch of the Galapagos, since the latter and New Caledonia lack woodpeckers. The feeding method of the woodpecker finch differs in that it stabs at grubs and levers them slowly out of the log using a small twig.
The nest of the New Caledonian crow is built high in a tree with usually 2–3 eggs laid from September to November.
Tool use and manufacture
This species uses stick tools in the wild by finding small twigs and probing them into holes in logs to extract
This species has a particular method for crafting tools:
Crows snip into the leaf edges and then tear out neat strips of vegetation with which they can probe insect-harboring crevices. These tools have been observed to come in three types: narrow strips, wide strips and multi-stepped strips—which are wide at one end and, via a manufacturing process that involves stepwise snips and tears, become narrow at the opposite end.[9]
The New Caledonian crow is the only non-primate species for which there is evidence of cumulative cultural evolution in tool manufacture. That is, this species appear to have invented new
The New Caledonian crow also spontaneously makes tools from materials it does not encounter in the wild. In 2002, researcher Alex Kacelnik and colleagues at the University of Oxford observed of a couple of New Caledonian crows called Betty and Abel:
Betty's toolmaking abilities came to light by accident during an experiment in which she and Abel had to choose between a hooked and a straight wire for retrieving small pieces of
This observation was further investigated in a series of studies. Out of ten successful retrievals, Betty bent the wire into a hook nine times. Abel retrieved the food once, without bending the wire.[3] The process would usually start with Betty trying to get the food bucket with the straight wire, but then she would make a hook from it bending it in different ways, usually by snagging one end of the wire under something, and then using the bent hook to pick up the tray.
Clearly, Betty's creation of hooks cannot be attributed to the shaping or reinforcement of trial-and-error behavior. In 2004, Hunt observed the crows in the wild also making hooks, but the adaptation to the new material of the wire was clearly novel and appeared purposeful. Intentional tool manufacture, even if it is generalizing a prior experience to a novel context, is rare in the animal world.
These crows also use tools to investigate potentially dangerous objects, such as a rubber snake or a flashing LED bike light.[11]
Meta- and compound tools
Meta-tool use is using one tool on another tool to achieve the objective of the task. It is generally considered to be a behaviour requiring more complex cognitive ability than the use of just a single tool. Studies show that New Caledonian crows are capable of meta-tool use, at a level rivalling the best performances seen in primates.[12][13][14]
One such study involved putting food in a box out of the crows' reach. The crows were given a stick that was too short to reach the food. However, this short stick could be used to retrieve a longer stick from another box, which could then be used to retrieve the food. This complex behaviour involved the crow realising that a tool could be used on non-food objects, and suppressing the urge to go directly for the food. It was solved by six of seven birds on the first attempt. This behaviour had previously only been observed in primates.
In a study conducted at the Max Planck Society crows have been shown to create compound tools from 2–4 short branches that could be slotted together.[15]
Mirror use
New Caledonian crows have shown they are able to process information from mirrors, a cognitive ability possessed by only a small number of species. By using a mirror, wild-caught New Caledonian crows are able to find objects they cannot see with a direct line of sight. However, the crows were unable to recognise themselves in the mirror – other corvids have tested positive for this capability.[16]
References
- . Retrieved 11 November 2021.
- ^ S2CID 4352835.
- ^ S2CID 29196266.
- S2CID 20717125.
- PMID 19654861.
- . Retrieved 12 August 2014.
- S2CID 8888382.
- ^ S2CID 22381110. Archived from the original(PDF) on 2008-10-16. Retrieved 3 May 2007.
- ^ John Pickrell (23 April 2003). "Crows Better at Tool Building Than Chimps, Study Says". National Geographic News. Archived from the original on April 24, 2003. Retrieved 3 May 2007.
- ^ Robert Winkler (8 August 2002). "Crow makes wire hook to get food". National Geographic News. Archived from the original on August 10, 2002. Retrieved 3 May 2007.
- ^ Davies, Ella (14 January 2011). "Curious crows explore with tools". BBC News.
- S2CID 20717125.
- ^ Randerson, James (August 17, 2007). "Crows match great apes in skilful tool use". The Guardian. London. Retrieved 17 August 2007.
- ^ Morelle, Rebecca (August 16, 2006). "Cleverest crows opt for two tools". BBC News. Retrieved 17 August 2007.
- PMID 30356096.
- BBC Nature. 20 September 2011. Retrieved 19 May 2012.
External links
- Oxford University crow research web site, including photos and movies
- From National Geographic: A video of the New Caledonian Crow making a hook out of wire (August 8, 2002)
- Tool use in crows is a combination of natural ability and schooling by other crows – LiveScience.com (October 31, 2006)
- BBC news website item about the New Caledonian Crow, includes video footage of tool use (August 16, 2007)
- Crow bends wire on purpose to lift bucket from glass tube (Nat'l Geo link no longer contains video).—YouTube