The Most Perfect Thing: Inside (and Outside) a Bird’s Egg

This book, like others by Tim Birkhead, is a journey through the history of a particular field of scientific exploration: in this case, the biology of eggs. Engagingly written and extensively researched, this book sets before us scenes from Yorkshire seabird colonies, Zambian tobacco farms and Soviet gulags, bringing to life the scientific process.

This book attempts to follow two paths. Firstly, it describes, and as far as possible explains, the main aspects of egg biology, from their formation, shape, colour, development, and the functions of the different parts. This information often serves to give context to our day-to-day observations; I was fascinated to learn that a clutch of Blue Tit eggs contain more calcium than the mother’s whole skeleton, which explains why she needs to forage for additional sources of calcium, such as mortar, grit and snail shells, while laying. The explanations of the timing of fertilisation, and of how tiny birds such as Goldcrests maintain the temperature of their eggs, are sure to be of interest to observers of bird behaviour, and the section on how eggs are defended against bacterial infection made me think again about the eggs in my kitchen!

Secondly, this is a story of the love of birds and eggs, particularly the author’s fascination with the breeding biology of Guillemots, a strand which runs through the book from beginning to end. The opening chapter describes the efforts of nineteenth century egg collectors to get their hands on the hugely diverse Guillemot eggs. I loved their descriptions of the different patterns – pepper pot, scrawl, green petal, black cap, shorthand – though I was disappointed not to find photographs of the beautiful patterns so well described in the text.

On occasion these two themes do not quite fit together, but mostly they dovetail beautifully. I particularly liked learning how the author’s research informed the chapters on egg colouration and recognition, including the results of painting a variety of odd geometrical shapes to match the colour and pattern of a particular Guillemot egg, and offering them to the parent bird.

This tour of scientific history does not shy away from the limits of knowledge, or attempt to tie up loose ends, instead emphasising where we have more to learn. I enjoyed the stories of wrong turns, such as the rather startling conclusion by Erasmus Darwin that some eggs are bright blue for camouflage against the sky when viewed through the ‘wickerwork’ of nest, which clearly shows that he had never seen the nest of a Song Thrush or Dunnock. The focus of this book is the process of discovery, ranging from tales of the author investigating the mechanisms of egg patterning by scrawling on an egg with a number of pencils tied together, to the value of long-term monitoring of breeding ecology. It is sure to be of interest to anyone with an appreciation of bird behaviour and biology, or the history of ornithology.

Book reviewed by Kate Risely

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