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Issue 257
November/December 2009
Resilience & Climate Change

Reviews

Jewels of Evolution
by

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Cover: White Snakes Head Fritillary Photograph: David Hall/WWT

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Jewels of Evolution

Lorna Howarth’s love of birds is enhanced by what must rate as one of the most fascinating books ever written on the subject. Consider the Birds: Who They Are and What They Do by Colin Tudge. Allen Lane, 2008. ISBN 9781846140976

This book is extremely well researched, astute, and rather funny too – a perfect recipe for an excellent read. It is clear from the start that Colin Tudge is in awe of avian evolution, and this passion for the subject imbues every page with insight and interest. He maps the evolutionary progress of birds, from the fossils of archæopteryx, through evolutionary dead-ends and extinctions, to the birds we are familiar with today. Their unique ability to travel long distances across vast oceans is a key driving force of their evolution, giving us the myriad species we see throughout the world.

Birds are a highly superior life form: they can fly. Tudge has always admired and envied birds for this very reason. If human beings wanted to fly like a bird (in the style of Icarus), then they would need a ‘keel’ that protruded two metres from their chests to anchor the necessary flight muscles. But evolution has not always worked entirely in birds’ favour: in order to fly, birds have to be relatively small. If the linear dimensions of a bird are doubled, their weight increases eight-fold. Consequently, very big birds are all land-bound, and this law of physics might explain why humans never evolved this remarkable trait.

However, just because most birds are small, it doesn’t mean they are all ‘bird-brained’ or unintelligent. It has been shown that many birds – crows, parrots, even the ‘secretary bird’ – are all highly intelligent; however, as Tudge states, the last still cannot take minutes! One of my favourite passages in the book is Tudge’s interpretation of birdsong. He doesn’t hesitate to say that “birds have language: not human language, but language full of meaning nonetheless” and he goes on to give a host of remarkable facts to underpin this statement. From the different dialects within the same species, to the elaborate calls of the Brown Thrasher, which has over 2,000 different ‘strophes’ or elements to its song, the section is endlessly fascinating.

A large part of the book is taken up with the classification of birds – a sterling feat indeed, as Tudge admits that “Nature feels no obligation to be easily definable”. This part of the book may be of more interest to hard-core ‘twitchers’ and ornithologists – so extensively researched and notated it is – yet always Tudge writes with humour and insight, so that even a lengthy passage on ratites is packed full of intriguing facts, for example that the elephant bird of Madagascar weighed almost half a ton and laid an egg over a foot long. Not one of the 450 pages can be skipped, for fear of missing a gem of information.

These fascinating facts include tales of pigeon ‘milk’ (a cheesy secretion stored in their crops to feed young) and other wonders, such as the male sungrebe who uniquely carries his babies in flight, in pouches of skin beneath his wings. Or of hummingbirds which can fly upside down and don’t hold their urine in bladders: they “spray as they go” so that they do not retain any extra weight that might interfere with their aerobatics.

Perhaps the saddest fact of all is that many of these magnificent birds Tudge traces from – the dodo to the moa – existed in exquisite harmony with their environment until humans came along and wiped them out. Now all we have left of them are a few fossil remains and the imagination of a man like Tudge, who brings them, momentarily, back to life. All is not quite lost though: the white-winged guan was thought to be extinct in 1870 but turned up again in 1977. And whilst the elephant bird is sadly not likely to reappear, some spectacular survival stories remain.

The passage on migration is also not to be missed. The author’s initial question, “How on Earth does a baby swallow hatched in Surrey know its way to Africa, after its parents have already left for warmer climes?”, remains unanswered, but much of this intriguing behaviour is revealed in all its complexity, and serves to underline just how different from mammals birds really are. Their intelligence is on another level to ours, and in many ways they are as highly evolved as humans; they can holiday in the sun every year without creating a huge carbon footprint!

Tudge presents an incredible picture of who birds are and what they do. Humbled by their feats of endurance, navigation, co-operation and ingenuity, reading this book means that I will never look at birds in the same way again. They are truly jewels of evolution. Most scientists agree that the ancestors of birds are in fact dinosaurs. For Tudge, dinosaurs are still with us, on duck ponds, in the farmyard and in the treetops. It pleases him immensely that the much-loved robin is probably a miniature dinosaur.

If only this review allowed space to elucidate further on the architectural abilities of the satin bowerbird who paints his ‘bachelor pad’ with the juice from berries and decorates it with sparkling trinkets, solely for the purpose of seduction. Or to delve into the clever tactics of birds who use human technology for their own purposes. But, alas, this review is already too long and there are two further points that Tudge makes which deserve mention.

We are still in thrall to the Darwinian evolutionary idea of “survival of the fittest” – in our competitive economies, our schools, and even our leisure – and yet birds demonstrate clearly that in fact survival of the most co-operative is the key to success. Tudge suggests we have much to learn from the birds and asks us to consider another theory of Darwin’s that has been rejected by the scientific community, but could yet allow a whole new understanding of the laws of Nature: that “a great number of animals have been rendered beautiful for beauty’s sake … and for no other purpose”.

Lorna Howarth is Co-editor of Resurgence.

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