Free Bird Sense by Tim Birkhead Page A

minuscule wings. They are odd; each like a flattened finger with a few feathers along one side and a curious hooked nail at the tip (what does it use that for?). Most remarkable of all are the kiwi’s tiny, all but useless eyes. Even if there had been one on the beach the previous night, the visual extravaganza of our bioluminescent cavorting would have been wasted on the kiwi.
    What is it like being a kiwi? How does it feel plodding through the undergrowth in almost total darkness, with virtually no vision, but with a sense of smell and of touch so much more sophisticated than our own? Richard Owen, a nasty narcissist but a superb anatomist, dissected one around 1830 and seeing the kiwi’s tiny eyes and huge olfactory region in its brain suggested – with little knowledge of the bird’s behaviour – that it relied more on smell than sight. Skilfully linking form with function, Owen’s predictions were elegantly borne out one hundred years later when behavioural tests revealed the laser-like accuracy with which kiwis pinpoint their prey below the ground. Kiwis can smell earthworms through 15 cm of soil! With such a sensitive nose, what does a kiwi experience on encountering another kiwi’s droppings – which to me at least are as pungent as those of a fox? Does that aroma conjour up an image of its owner?
    In his famous essay ‘What is it like to be a bat?’ published in 1974 , the philosopher Thomas Nagel argued that we can never know what it feels like to be another creature. Feelings and consciousness are subjective experiences so they cannot be shared or imagined by anyone else. Nagel chose the bat because as a mammal it has many senses in common with ourselves, but at the same time possesses one sense – echolocation – that we do not have, making it impossible for us to know what it feels like. 1
    In one sense Nagel is right: we can never know exactly what it’s like to be a bat or indeed a bird, because, he says, even if we imagine what it is like it is no more than that, imagining what it is like. Subtle and pedantic perhaps, but that’s philosophers for you. Biologists take a more pragmatic approach, and that’s what I’m going to do. Using technologies that extend our own senses, together with an array of imaginative behavioural tests, biologists have been remarkably good at discovering what it is like to be something else. Extending and enhancing our senses has been the secret of our success. It started in the 1600 s when Robert Hooke first demonstrated his microscope at the Royal Society in London. Even the most mundane objects – such as a bird’s feather – were transformed into something wondrous when seen through the lens of a microscope. In the 1940 s biologists were amazed by the details revealed by the first sonograms – sound pictures – of birdsong, and even more amazed when in 2007 for the first time they were able to see – using fMRI (functional magnetic resonance imaging) scanning technology – the activity in a bird’s brain in response to hearing the song of its own species. 2
    We identify more closely with birds than with any other group of animals (apart from primates and our pet dogs), because the vast majority of bird species – although not the kiwi – rely primarily on the same two senses as we do: vision and hearing. In addition, birds walk on two legs, most species are diurnal and some, like owls and puffins, have human-like faces, or at least, faces we can relate to. This similarity however, has blinded us to other aspects of birds’ senses. Until recently it was assumed – with the kiwi as a quirky exception – that birds have no sense of smell, taste or touch. As we will see, nothing could be further from the truth. The other thing that has retarded our understanding of what it is like to be a bird is the fact that to comprehend their senses we have no alternative but to compare them with our own, yet it is this that so limits our ability to understand other