A new tool-using bird to crow about
Published online: 31 March 2017
The Author(s) 2017. This article is published with open access at Springerlink.com
Summary The Hawaiian crow has been revealed as a skilled
tool user, confirmed by testing the last members of this endan-
gered species that survive in captivity. The finding suggests its
behavior is tantalizingly similar to that of the famous tool-
using New Caledonian crow and has implications for the evo-
lution of tool use and intelligence in birds.
Keywords Tool use
Tool use is often singled out as a defining feature of humanity.
However, many other animals have independently evolved
technological skills. They are phylogenetically widespread yet
occur at low frequency within different animal groups. Why
should some species evolve tool use but not others? Various
preconditions are proposed: cognitive, environmental, anatom-
ical, behavioral, and genetic. Primates and birds probably
shared some key features that enabled their tool skills to evolve
in parallel. Intelligence, behavioral flexibility, and innovation
are just a few possibilities. Corvids, with relatively large brains
and impressive cognitive abilities, are prime candidates to
evolve technology. One such corvid is the New Caledonian
crow (Corvus moneduloides), whose tool-making talents rival
those of our close relatives (Hunt & Uomini, 2016).
Rutz et al. (2016) report that the Hawaiian crow (Corvus
hawaiiensis) is also a tool-using species. Sadly, the Hawaiian
crow is extinct in the wild. The world’s population is sustained
in two breeding facilities in the hope they can eventually return
to the wild. From previous work with New Caledonian crows,
Rutz and colleagues predicted in 2011 that Hawaiian crows
should be tool users (Rutz & St Clair, 2012). Meanwhile, the
Hawaiian crow keepers had commonly observed tool use in
their crows. They began collaborating in 2012. The fact that
this publication was 4 years in the making testifies to the exten-
sive research the team carried out to explore some of the key
factors underpinning Hawaiian crow tool use. We focus here on
innovation, genetic basis, and social transmission.
Rutz et al. (2016) tested captive Hawaiian crows with the
same tool-use tasks as those given to New Caledonian crows:
natural logs with meat in holes that could only be reached with
suitably long tools. About 90% of adult crows and 40% of juve-
niles used twigs to successfully extract the food (81 of 104 birds).
videos show that adult crows chose tools of appropriate length or
shortened overly long twigs. However, unlike New Caledonian
crows, the Hawaiian crows did not appear to standardize their
tools, as they used plant materials of many sizes and shapes.
The Hawaiian crows were already familiar with tools, for
example to fish food from their water bowls with sticks.
Because tool use is known only in these captive birds, it is
possible that the behavior was an innovation by one or more
smart birds. Such innovation was documented in a crow rela-
tive that does not use tools in the wild, the rook (Corvus
frugilegus), which spontaneously used tools to get food in
captivity. However, that most adult Hawaiian crows success-
fully solved the log task suggested an inherited disposition for
tool use, similar to that in the New Caledonian crow.
To find out if Hawaiian crows’ technological skills had a
genetic basis, Rutz et al. (2016) reared seven juveniles deprived
of social contact to other tool users (crow and human). These
juveniles readily manipulated objects and tried to reach inac-
cessible food with them. However, they spent less time
* Natalie Uomini
Max Planck Institute for the Science of Human History, Kahlaische
Strasse 10, 07745 Jena, Germany
238 Meola Road, Auckland 1022, New Zealand
Learn Behav (2017) 45:205–206