Only a handful of bird species are known to use foraging tools in the wild1. Amongst them, the New Caledonian crow (Corvus moneduloides) stands out with its sophisticated tool-making skills2,3. Despite considerable speculation, the evolutionary origins of this species’ remarkable tool behaviour remain largely unknown, not least because no naturally tool-using congeners have yet been identified that would enable informative comparisons4. Here we show that another tropical corvid, the ‘Alalā (C. hawaiiensis; Hawaiian crow), is a highly dexterous tool user. Although the ‘Alalā became extinct in the wild in the early 2000s, and currently survives only in captivity5, at least two lines of evidence suggest that tool use is part of the species’ natural behavioural repertoire: juveniles develop functional tool use without training, or social input from adults; and proficient tool use is a species-wide capacity. ‘Alalā and New Caledonian crows evolved in similar environments on remote tropical islands, yet are only distantly related6, suggesting that their technical abilities arose convergently. This supports the idea that avian foraging tool use is facilitated by ecological conditions typical of islands, such as reduced competition for embedded prey and low predation risk4,7. Our discovery creates exciting opportunities for comparative research on multiple tool-using and non-tool-using corvid species. Such work will in turn pave the way for replicated cross-taxonomic comparisons with the primate lineage, enabling valuable insights into the evolutionary origins of tool-using behaviour.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
We thank: the many people – far too many to name individually – who have prevented the ‘Alalaˉ’s extinction, and who are working tirelessly towards its successful reintroduction into the wild; R. Fleischer for facilitating initial contacts; San Diego Zoo Global’s staff for assistance with experiments; C. Higgott for help with video scoring; D. Parker for constructing the consensus phylogeny; several photographers for providing images for Fig. 1; S. Thompson for help with graphic design; and G. Ruxton for statistical advice. Research was conducted with permission from San Diego Zoo Global’s IACUC animal welfare committee (Project ID#12-017), and with funding from the Biotechnology and Biological Sciences Research Council, UK (BBSRC; grant BB/G023913/2 to C.R., and studentship to B.C.K.), the University of St Andrews (C.R.), JASSO (S.S.), and the Royal Society of London (M.B.M.). Funding for the captive ‘Alala¯ propagation programme was provided by the U.S. Fish and Wildlife Service, Hawai‘i Division of Forestry and Wildlife, Moore Family Foundation, Marisla Foundation, several anonymous donors, and San Diego Zoo Global.
Extended data figures
This unedited scene shows the first presentation of the log set-up to adult male #134 (21 January 2013). Note that the log is a prototype that, compared to the final design later used for the species-wide behavioural assay, contained two additional holes.
During experimental trials, many ‘Alalā were observed: a, to choose tools of appropriate dimensions; b, to replace tools that were not suitable; c, to transport non-supplied sticks to the set-up to be used as tools; to modify tools d, before or e, during deployment; or f, to handle, try and modify several different sticks during an extraction attempt. Tool manufacture behaviour included: g, snipping-off twigs from supplied dead branches; the production of h, bark flakes and i, wood splinters; and j, successive subtraction of material from non-supplied live plant material.
Functional tool behaviour can result from (a combination of) genetic predispositions, social learning, and individual learning. To investigate the relative importance of different processes, ‘naïve’ juveniles can be reared in captivity without opportunities to observe tool-use behaviour in proficient adult conspecifics, or even in humans. Under such controlled conditions, ‘Alalā chicks develop functional tool use over the first few months of life: a, first handling and carrying objects, including sticks, stones and other items; before b, inserting them into holes and crevices with gradually increasing proficiency (here, during a probe trial with several baited extraction tasks presented on a ‘platform’).
Before the commencement of systematic behavioural experiments, staff at the KBCC and MBCC facilities had regularly observed ‘Alalā using tools. Following these opportunistic observations, on the 28 July 2011, four different birds were filmed using tools to reach for bait placed in a water bath (#114, #118, #135), or behind wire mesh (#146).
Like New Caledonian crows, ‘Alalā have unusually large eye-movement amplitudes. This video was taken when adult male #121 was trapped for a routine pre-breeding health check (19 March 2015) and presented with a neonate mouse to attract its attention.
Tool use of an adult male a, ‘Alalā and b, New Caledonian crow. ‘Alalā tend to hold stick tools in a frontal grip whereas New Caledonian crows prefer a transverse grip. c, Naturally non-tool-using rooks can be trained to use tools, but compared to most ‘Alalā and New Caledonian crows, they appear to handle sticks less dexterously (but note difference in extraction tasks provided).
About this article
Behavioral Ecology and Sociobiology (2018)