Clever crows rely on a unique bird's eye view

Interviewer: Andy Tootell (Ideas Lab)
Guest:  Dr Jackie Chappell
Recorded: 22/10/2012
Broadcast: 22/10/2012

Andy: Hello, and welcome to this Ideas Lab Predictor podflash which is an extra bit of information in addition to our regular podcast series.   I’m sat here with Dr Jackie Chappell who’s Lecturer in Animal Behaviour in the School of Biosciences at the University of Birmingham and she also runs the Cognitive Adaptations Research Group. Hello Jackie. 

Jackie: Hello.

Andy: Now we spoke to you in June 2010, you were our second ever podcast interviewee and at the time you were talking about intelligence in New Caledonian crows and how they can use tools to forage for food. Now you’ve just released some new research along with colleagues at St. Andrew’s and the University of Oxford which sort of builds on this and you’ve discovered that it’s not just about the intelligence. 

Jackie:  Yes, that’s right.  One of the really puzzling things about New Caledonian crows is why they’re the only member of the crow species to actually make and use tools in the wild.  Other crow species have been shown to be quite capable of using tools in captivity so there was an experiment that was done at the University of Cambridge using rooks to show that they could also bend wires in order to make a hook and pull food up from a bucket.  So we know that intelligence can’t be the whole story why there's this striking difference between New Caledonian crows and other species.  So we started to look at other factors, physical factors that might mean that New Caledonian Crows were more able to use and make tools than other crow species and so given that crows have to actually hold a tool in their bill – this is quite a difficult task – we thought that was a good place to start.  If you think about it, it’s quite a difficult thing for crows to do. When we use tools we can move our hand around independently of our eyes but crows have their hand if you like attached to their eyes so it’s like having your eyes mounted on the back of your hand when you’re trying to use a screw driver and it’s quite a difficult thing to do and if you want to use tools efficiently, you have to be able to both see what the end of the tool is doing so that you can control it properly, but also have a stable grip on it too so that you can really hold it precisely. And so what we did was we had a look both at the bill shape of New Caledonian crows but also at their visual field to see whether or not they could see what was going on with the tip of the tool and what we found when we looked at New Caledonian crows and a number of other species, crow species, so this is in the same genus Corvus that includes New Caledonian crows, so that’s things like ravens and carrion crows and rooks, and we found that New Caledonian crows were the only ones who had a very straight bill and also had a lot of overlap between the visual fields of each eye, which meant that they had an area where the visual fields overlapped – a so-called binocular sector.  And this was broad enough to encompass the tip of the tool when they’re holding it and that was helped by the fact that they had a very straight bill because that meant that they could hold the tool with one end of it pressed against the side of their head, much the same way when you hold a pencil you steady it, and still see the tip of the tool in this binocular field. 

Andy: When you’re talking about the straightness of the bill, that’s something you can see, you can look at a bird and you can see the differences and shapes of their bills. How did you determine the breadth of the crow’s vision?

Jackie: Well it’s a very nice technique that was developed by Professor Graham Martin who also was at this university who’s now retired and he’s done a lot of work looking at visual fields of various bird species and actually what you do is you use something called an ophthalmoscope. So if you’ve ever been to the optician to get your eyes tested you know that they shine a light into your eye and look through this apparatus to look at your retina and that’s essentially what we’re doing with the birds. So we put the birds into an apparatus that holds the bird firmly and holds their head still, most importantly, and then systematically go around using the ophthalmoscope to shine a light in the eye and look at the eye from a number of different angles so that you can see how big the retinal field is and when the field of one eye overlaps with that of the other and that way you can get a good idea of what the visual fields are like from all around the bird, above and below it as well. 

Andy: So where is your research going to go next? What are you going to be looking at? Are you going to be building on this research or looking at something entirely different, or another bird maybe?

Jackie: Probably other birds.  I mean one of the main things that I’m interested in is the way in which animals understand their physical environment but in order to understand what’s going on in the bird’s head or other species - I’m also interested in primates and humans – so in order to understand how individuals are processing information from the environment you have to know how they’re getting information in. So you have to understand about their perception and with humans that’s not too difficult because we’re looking at another individual who’s very like ourselves but if you’re looking at birds for example, it can be very difficult to know where they’re looking because they have their eyes generally on the sides of their heads and so we really need to know more about their perception in order to understand how that can both enable but also constrain what they can learn from the environment.  So we’ve also done some similar work on parrots looking at their visual fields because we wanted to know whether or not parrots can actually see objects that they’re holding in their bill because they do a lot of exploration of objects that we suspect might be involved in learning about properties of materials and this kind of thing and what we found to our surprise actually was that they can’t see what they’ve got in their bill. They can see it when it’s in their foot, when they bring it up to their bill, but they can’t actually see what’s in their bill and so what we suspect is going on is that they’re using their visual fields before they bring it up there but they’ve got other sensory apparatus in their bill, they’ve got a touch sensor in their bill tip which was something that was known about many years ago but has kind of been forgotten, and they probably use that rather than their eyes when they’re actually exploring something in their bill itself together with their tongue which is very responsive and muscular. So it’s quite interesting working out what their sensory world is. 

Andy: Well it sounds like plenty more fascinating research in the pipeline to keep you busy. I wish you all the very best of luck with it and hopefully we can catch up with you again in the future and thanks very much for joining me today.

Jackie: Thanks very much.