Crows use mirrors to find food
Clever New Caledonian crows can use mirrors to find food, according to scientists.
Researchers from the University of Auckland, New Zealand, tested wild-caught crows' reactions to mirrors.
The crows did not recognise themselves but found cached food items by studying their reflections.
The results put the birds in an elite group of species - which includes primates and elephants - known to be able to process mirror information.
End Quote Felipe S Medina Rodriguez University of Auckland, New Zealand
New Caledonian crows can process mirror information in a primate-like fashion”
New Caledonian crows (Corvus moneduloides) are known for their intelligent and innovative use of tools, such as twigs, which they use to fish nutritious insects out of holes and crevices.
Mirror experiments with other members of the same family of birds, the corvids, have found that magpies recognise their reflections but jungle crows do not.
In this study, published in the journal Animal Behaviour, psychologists examined the recognition skills of the notoriously clever New Caledonian crows.
Scientists captured 10 wild birds and placed them in large cages in order to record their behaviour in response to mirrors.
All the crows reacted to seeing their reflections as if they were encountering another crow; the birds made rapid head movements, raised their tails and even attacked the reflection.
Lead researcher Felipe S Medina Rodriguez said the crows' antagonistic reaction to their mirror image "was not surprising". He explained that an animal usually had extensive exposure to mirrors before it began to display an understanding that the image it was seeing was itself.
When the crows moved away from the mirror and lost sight of their reflection, they frequently searched behind the mirror to locate the "other" bird.
ANIMALS ON REFLECTION
- Chimps in captivity have demonstrated self-recognition, using mirrors to explore unseen parts of their bodies
- Trained dolphins not only recognise themselves in mirrors but notice changes in their appearance, displaying a sophisticated sense of self
- Magpies and Asian elephants have also passed the "mark test" to show an understanding of their reflection by touching marks on their body that are only visible in a mirror
The researchers think that the behaviour was probably caused by the birds' lack of experience of mirrors; similar reactions have been recorded in primate infants and two-year-old children.
The second part of the experiment, though, revealed some surprising findings.
The scientists devised a task to test whether the crows could use mirrors to locate cubes of meat that were hidden from direct view.
All of the crows tested appeared to understand how the meat's reflection correlated to its location.
"We were surprised by how quickly the crows learnt to use a mirror reflection to locate hidden food," said Mr Medina.
"Usually, it takes longer for an animal to start using the properties of mirrors to have access to otherwise non-visible objects."
Some of the crows were more adept than others, and Mr Medina suggested that the difference in ability proved that they were not using their sense of smell to find the food.
"Importantly, our best crow, a female juvenile called Obo, was not able to find the food when the mirror was reversed. This showed that the crows were probably solving the problem by relying exclusively on the visual information available in the mirror," said Mr Medina.Wild skills
- New Caledonian crows have displayed advanced tool-using skills. They are able to combine a number of tools to solve one task and have been found to teach their offspring these skills
- Outside of the lab, their corvid cousins, the magpies, use their nous to survive in the urban environment. They can spot humans that might pose a threat
- African grey parrots are the only birds that appear to be even smarter. They have been tested in a variety of problem-solving tests and show such advanced mental abilities that they choose whether to work together or alone
Previous studies have shown that African grey parrots, great apes, dolphins, monkeys and Asian elephants all share our ability to process mirror information.
But according to Mr Medina, the New Caledonian crows are unique in the group because they are wild animals.
"These animals are usually kept in highly enriched environments, and have been subject to prolonged human contact and training," he told BBC Nature. "[So] we cannot know how much of their problem solving skill comes from their intensive experience in captivity and human experimentation and how much would develop naturally in the wild.
"What our study has now revealed is that wild-caught New Caledonian crows can process mirror information in a primate-like fashion, and that this ability develops very quickly without extensive mirror exposure."
New Caledonian crows are named after the islands on which they are found in the South Pacific Ocean to the east of Australia and north of New Zealand.Heads together
Scientists have also recently been investigating the intelligence of another well-known bird family: the tits.
In a study published in the Proceedings of the National Academy of Sciences, researchers from Oxford University, UK, looked at the problem-solving abilities of great tits (Parus major) and blue tits (Cyanistes caeruleus).
Food dispensers that required the birds to pull a lever in order to receive a reward were placed in woodlands as "puzzles" for the birds.
Dr Julie Morand-Ferron and Dr John Quinn found that larger, mixed-species flocks of the birds solved the problems more quickly and efficiently than smaller groups of birds.
The zoologists suggested that larger groups were more likely to contain a "skilled individual" that could operate the device for the benefit of the whole group.
"For these social songbirds, 30 heads are almost always better than 20, and 20 better than 10, when it comes to solving problems," said Dr Morand-Ferron.
"Previous research has suggested that this effect, sometimes called the 'pool of competence' occurs in humans, but this is the first direct evidence that a similar effect occurs in non-human animals."
Great tits and blue tits highly social birds that are found in a variety of different habitats across Europe.
"It may be that in species that are always looking to move into new areas, and so confront new problems, there are many benefits to being in a gang with individuals with different skills and personalities," explained Dr Morand-Ferron.