Making sense of birds
Date: April 7 2012
BIRD SENSE: What It's Like to Be a Bird. By Tim Birkhead. Bloomsbury. 265pp. $35. Reviewer: IAN FRASER
With this book Tim Birkhead has confirmed himself as one of the best English language writers on the science of ornithology in the world today - at least, he's my favourite. As professor of behavioural ecology at Sheffield University he is clearly qualified to write about his topic, but equally importantly he has an exquisite gift for telling stories of science that laypeople can be enthralled by. His previous book, The Wisdom of Birds, was a history of the study of birds from Aristotle to the present day, and was a remarkable achievement.
Bird Sense is equally ambitious in its own way, seeking to provide an ''accessible account of the senses of birds'', examined in separate chapters on seeing, hearing, touch, taste, smell, magnetic sense and, perhaps controversially, emotions. He draws on his experiences in often rugged field work from remote Atlantic islands to New Zealand rainforests to arid Namibia to illustrate his topics with pertinent and entertaining anecdotes, boldly scanning the range of concepts that a consideration of each sense involves. As revealed in The Wisdom of Birds, one of his areas of especial interest is the history of science and again we explore with him the development of knowledge of the multifarious fields of the study of bird senses, bringing to life researchers, from the Middle Ages to today, to whom he and we are indebted. At the same time it is surprising to discover, in many of the topics considered, how much there is still to learn.
Perhaps the subtitle is a little overambitious, indeed slightly misleading, when even more specific questions are posed in the preface: ''What is it like for an emperor penguin diving in the inky blackness of the Antarctic seas?''; ''What is it like to be a flamingo sensing invisible rain falling hundreds of kilometres away?'', etc. We can't ever know that - we can't even really know what ''it's like'' to be another human - but what Birkhead does well is help us understand how they do it, and how we know how they do it.
To his scientific knowledge and communications skill is added his creativity; in the chapter on touch he explores topics which include the amazingly sensitive ''bill tip organ'', preening, filoplumes (bristly feathers whose role is to detect movement in other feathers and realign them), the brood patch (the bare patch on a brooding female's breast, which among things gives her information as to when to stop laying more eggs), and the touch-sensitive patches on a blind baby cuckoo's back, which recognise - and evict - host babies and eggs. The extraordinary bill tip organ enables a duck to strain mud and retain tiny food items while rejecting debris, by instantaneous touch alone. Also in the chapter on touch, Birkhead explores the intriguing question as to whether birds enjoy sex … In that context, the question of the purpose of the male red-billed buffalo-weaver's strange ''false penis'' is one you may wish to explore in private. Another example of his lateral thinking is found in the chapter on taste, where in addition to the obvious questions, he examines birds which themselves taste bad.
The world of birds is truly wonderful, and this book reveals many wonders, such as the significance of ''sidedness''; for example, chick embryos in the egg before hatching turn their head to the left, so most light is perceived by the right eye; chicks from eggs developed in darkness are much less competent at multi-tasking, that is, finding food (with the right eye) while watching for predators (with the left). And parrots with the strongest bias to always using the same foot are also best at problem-solving.
A corncrake (a European dryland ''wader'') called into his ear at point-blank range - Birkhead was lying in a paddock at night at the time, as you do - at 100 decibels, enough to damage his hearing after about 15 minutes. Why then does the bird not deafen itself? Because it has a reflex that reduces the sound of its own voice. Furthermore, even if its inner ear (or cochlea) was damaged, it would recover. In mammals the lining of the cochlea is covered with hair cells, which convert pressure waves to ''sound signals'' passed to the brain; once damaged, ours don't recover - birds just replace theirs. Bird brains also shrink and grow with the seasons, so that, for instance, in winter the song-creation and -receiving sector of the brain shrinks dramatically, thus reducing energy costs. Studies in Europe show that birds have had to adapt to city living by increasing the volume of calls; Berlin nightingales sing 14 decibels louder than their country cousins (roughly three times as loud), and crank it up further during rush hour.
Birkhead's own sense of wonder is refreshing; he says of the North American great grey owl: ''Its ability to pinpoint a mouse, invisible under the snow, by means of asymmetric ears, leaves me speechless.'' The asymmetry refers to the fact that one ear opening is higher than the other, to better pinpoint a sound source.
The final chapter on emotions is both frustrating, because it carries the least hard information, and beguiling. In what way do birds experience pain? Do they have an emotional response to loss? We know how birds respond to stress, but how do they experience it? Does love have any meaning to a bird which mates for life? This is a practising scientist asking the questions, so they warrant attention.
Birkhead reports there was relatively little interest in researching the subject until recent decades. That has changed, and the final sentence of the book is an exciting one for those who are interested: ''At the present time we have a good basic understanding of at least some of the senses of birds, but the best is yet to come.'' When it does, I hope that Tim Birkhead is there to report on it.
Ian Fraser is a local naturalist, broadcaster and author, whose most recent book is A Bush Capital Year.