What is it like to be a bird?


Cover of Tim Birkhead’s book Bird Sense

Can we ever know what it is like to be a bird? As poetic as the question may appear to be, it’s fascinating how the question has captured the attention of a bunch of  scientists, artists and other professionals ranging from neurosurgeons, ecologists, physiologists to bird illustrators and medieval travellers. The fascination with bird flight is possibly as old as language itself. Birds are among the early cave paintings, be it in the subterranean caves discovered by teenage boys at Lascaux, or the paintings of Genyornis in cave paintings in Northern Australia that could be 40,000 years old, dating to the time when man set foot on that continent. In Bird Sense, Tim Birkhead who has written fascinating stuff on history of science, birds and birdwatching and has edited the Cambridge Encyclopaedia of Ornithology, makes a narrative synthesis of the historical and contemporary knowledge on what it is like to be a bird. An extremely intriguing question throwing up questions such as “Is this know-able?”. Such philosophical meanderings have clearly not deterred several scientists from designing simple and elegent experiments to try and understand this.

The book begins with a set of questions that Birkhead claims the book will answer. Just seeing the list captivated me to start reading the book (see video intro by Tim Birkhead below, where he outlines some of the questions he attempts to answer in the book). The chapters, organised according to the five senses that we know – seeing, listening, smell, taste and touch – and two of which we don’t know fully understand (at least among birds!), magnetism and emotions – are a treasure of stories of early anecdotes and discoveries.

440px Satin Bowerbird nest

Satin Bowerbird’s Blue nest (Photo from Wikimedia Commons)

The chapter on seeing begins with the attempts of early falconers in Europe attempting to perform experiments with shrikes to understand the range of falcon’s vision. Among these early experiments, the falconers of Valkenswaard in Netherlands stand out. Falconry, with its possible origins in Central Asia matured in the middle-east, eventually tracing northwards to Europe. In the book, the experience of English naturalist and falconer, James E. Harting, who was supposedly very often seen in London with a hawk on his fist, and known for his experiments in a falcon hunt in 1877, where traditionally migratory falcons used to be trapped, are described. Later studies on the structure of the eye particularly the cellular structure of the retina and the fovea, the high-density receptor pit on the retina, are described in a beautiful story. The story of Casey Albert Wood, an ophthalmologist who was also interested in the eye of birds (among other animals) is described, how he pored into early literature on avian sight by falconers [As an aside, Wood has no article (yet) on the English Wikipedia (the Dutch one has an article though) and the scarce material on him on the Internet I went through include an inventory of his items handed over to the Osler Library of the History of Medicine at McGill University, Canada. This interesting inventory includes some of his contributions to the New York based Charaka club – see the proceedings on Archive.org]. The structure of the eye has been an object of great fascination from historical times, the debate spilling over to the contemporary creationism-evolution debates, with creationists often drawing from William Paley’s flawed teleological arguments in favour of a creation or being inspired by the intricate structure of the human eye to infer irreducible complexity and hence an intelligent designer. The fact that we see with our brains rather than our eyes is illustrated by recalling an extreme experiment of getting used to image-reversing glasses while riding a bike, an unreal experiment actually carried out by Irwin Moon in 1961 [turns out though that the good Dr. Moon was a man of God though]. Later on beautiful stories of bird gifts to one of those Louis kings and expeditions to understand lekking behaviour of a curiously named South American bird, the cock-of-the-rock and the Bowerbird’s decorative nests are used to convincingly tell us the story of sight in birds. Darwin’s ideas regarding how female preference for colourful birds (as a proxy of reproductive success) could have driven run-away evolutionary processes culminating in peacocks train of colourful feathers and such are described. Pierre Broca and his work find mention. He was known for his discovery of the hemispheric nature of control over our speech through dissection of the brain of a man with a speech defect who succumbed to Syphilis.This led him to conclude that the disease-mediated damage to particular hemispheres of the brain could have led to the speech defect; wonderful stories that are missed out in textbooks of medicine, for example. Quite recently, this aphasic brain of the man who couldn’t speak too much was identified to belong to Louis Victor Leborgne, possibly one of the most famous patients of the last century, in an article in the Journal of the History of the Neurosciences. The consequence is the amazing phenomenon of lateralisation or “sidedness” in birds [see lateralisation in bird song as well as in flight path], which for a century was supposed to have been thought to be unique for humans. Apparently, such sidedness among birds could be both at the level of individuals, wherein some individual parrots’ bill use or leg preference for tool use by those extremely intelligent New Caledonian crows. Similarly, entire species could exhibit a sidedness too; the Peregrine Falcon which swoops down upon its prey along a wide arc mainly use their right eye!

On hearing in birds, Birkhead begins with an illustration of hearing among Barn Owls, which can hunt in near darkness. The chapter progresses to describe arly explorations as to how particularly loud birds (listen to the extremely loud corncrake or the capercaillie) protect their own hears from damage of their nearly 150db calls. Later on, he touches upon the recent work on songs which blur the black-and-white nature-nurture debates and divides prevalent in the last century. The story of birds songs beautifully shows us how learning and genes are intricately involved with each other in manifesting what we see, this perhaps being a phenomenon across taxa, including humans. Later on, while describing the historical work done on the inner ear, the story of the Swedish physician and anatomist, Gustav Retzius, whose pioneering work on illustrating inner ears of several species including birds led to great insights into hearing in general (and among birds too). In spite of his geographical proximity (he was a Swede!) and a 12-time nomination, apparently he didn’t get a single one, possibly the Ivan Lendl among the Nobels! (Retzius did some work on botany, embryology, histology and craniometry, talk the modern specialisation fad within medicine let alone in science!). The ability of avian hair cells to regenerate and the asymmetrically placed ears in owls and how this helps 3-d localisation of prey is beautifully described. In fact, hearing is quite sophisticated among birds; nightingales in Berlin supposedly sing a good 14db louder to make up for the noise, while Birkhead in a subsequent section wonders if the introduced Dunnocks and Blackbirds in New Zealand’s relatively silent forests sing softer. The early hypothesis of Hamilton Hartridge on whether bats could be using high frequency sounds to echo-locate and the subsequent experiments conducted by the (then) Harvard undergraduate, Don Griffin on oilbirds which also navigate in total darkness [see and hear Oilbird echolocation in the dark] and finding that they also use echolocation are beautifully woven into a story.

Touch in birds is the most under-recognised function. Using examples of the false-penis among red-billed buffalo weavers (which by the way could also be “experiencing” an orgasm; see Birkhead’s article!) and the bristles of the nightjar the way birds touch is explored. Early work by German anatomists on the receptors in duck’s bill seems to have been key to our appreciation of how much touch is important in many birds and how precise it could be. Corpuscles for touch of two types arranged “beautifully” are described; one named after the Belgian biologist Grandry (for whom I neither found a Wikipedia entry nor a first name yet!) and the other named after the German histologist Emil Herbst [see article on anatomy of bill tip co-authored by Tim Birkhead again]. The behaviour of allo-preening wherein birds preen each other and the one study among ravens in 2008 by Stowe and colleagues, that shows stress reduction (measured by blood cortisol levels, a hormone situations of high stress) in response to allo-preening illustrate the degree of touch sensation among birds.

The chapter on hearing begins with John Weir’s early experiments with offering possibly unpleasant tasting bright caterpillars instead of the cryptic ones that birds were eating and how the birds found these “distasteful”, an experiment he is supposed to have performed at the behest of Alfred Russel Wallace and Charles Darwin, following up on their own fascination with colouration in animals. Apparently, taste in birds was a hotly debated topic in Darwin’s day and age, although clearly Darwin and his ilk were quite convinced of it and the role it has played in the evolution of mimicry seems to have been clear to them. Among all the relatively older historical anecdotes, the more contemporary one that happened to Bruce Beehler (known locally for his work on Indian birds and biogeography with Salim Ali and Dillon Ripley), whose PhD student Jack Dumbacher found in late 80s and early 90s, the first-ever distasteful bird, the New Guinean hooded pitohui (pit-oh-wheez), because of its toxic feathers. On hearing this, Beehler is supposed to have exclaimed that this could be the cover of Science magazine, which it seems it did with a cover photo of Science in October 1992! Like in many such instances, this piece of information was quite well known to the local people who had in fact named the bird wohob, bird whose bitter skin puckers the mouth! Turns out from Dumbacher’s future work that the toxin in the birds feathers comes from its diet of melyrid beetles and is a kind of batrachotoxin, now known to be stronger than strychnine. Other birds in New Guinea are now known to be similarly toxic. Their experiments, of course being much more sophisticated than Audubon’s “experiment” of feeding ten boiled carcasses of Carolina Parakeets to cats to see if they are unpleasant or toxic!

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Cover of the October 1992 issue of Science magazine with the Hooded Pitohui

The chapter on smell explores the amazing capacity of the Kiwi to smell earthworms inside the soil. Experiments seem to have focused on whether the Kiwis hear the worms or smell them when they dig into the soil. The chapter also explores sense in birds through the early life of the “larger-than-life” bird illustrator, John James Audubon, who was, as the book describes “a dynamic, erratic and charming illegitimate son of a French sea captain and a servant girl” born in Haiti. Audubon’s initial article “exploding” the then held belief that American Turkey-buzzard smelt carrion, and instead declarign though his experiments that they actually saw carrion sparked a lot of interest on the ability to smell among birds. It turns out that Audubon’s experiments were actually flawed and indeed, the buzzards do indeed have a sense of smell, one of the explanations being that Audubon might have mis-identified (or mis-reported?) Turkey-vultures, a similar looking species as Turkey-buzzards. It seems the former does have a poor sense of smell….talk of bad identification by the veterans! Like in many cases with birds (and biology!), it was somebody in the “medical” community to the rescue. Birkhead attributes a lot of progress in the study of avian olfaction to an medical illustrator in Johns Hopkins, aptly named, Betsy Bang, with her article in Nature in 1960 focusing on avian olfaction. Later on in the chapter, the unexpectedly good ability of sea birds such as albatrosses in smelling is also described though long stories and experiments that showed this.

The last two chapters, one on magnetism and the other on emotions are relatively less “developed” than the above five, possibly showing the dearth of work on these two. That said, the chapter on magnetic sense in birds begins with a fascinating of work done by the famous British ecologist, David Lack, then a school teacher and Ronald Lockley on islands and their experiments with taking away birds and releasing them far away and how long it took for the birds to return to the island. With better technology, the sense of direction in birds and how they possibly “sense” earth’s magnetic fields has improved but it is one of these those things that we will never fully appreciate, because of our own sense of not being able to know what it is like to sense this. The last chapter on emotions gives some insights into social behaviours among birds.

All in all a great read both for a lay reader and possibly for the sciency ones. A great introduction to several hundreds of years of experiments and stories about birds and their senses.

An edited version of this blog appeared on Conservation India | Bird Sense Review by daktre

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