The Most Perfect Thing: inside (and outside) a bird’s egg

Published on 13 April 2016 in Book reviews

EggsBy Tim Birkhead; Bloomsbury, 2016

Hbk, 288pp; eight pages of colour photographs, line-drawings

ISBN 978-1-4088-5125-8 BB Bookshop price £16.99

Given the track record of the author I was expecting this to be an enjoyable and informative read, and I was far from disappointed. He has the happy knack of weaving stories together that hold the attention, imparting knowledge gently, with satisfyingly little effort required on the part of the reader. A few of the sections that deal with the complex processes involved in egg formation and chick development inevitably require some technical detail and perhaps demand a little more concentration but at no point does it become turgid or dull.

The book deals with the biological mechanisms involved in egg production and development, as well as the evolutionary aspects as to why things are as they are – the how as well as the why as he puts it. I found both to be equally engaging and was repeatedly surprised by the insights provided in areas I thought I knew better. To take just one example that stuck in my mind: the redoubtable Goldcrest Regulus regulus lays large eggs in relation to its body size and is simply too small to incubate an entire clutch effectively in the normal manner. It gets around this by lining its tiny nest especially well with feathers and moss to retain heat and, most amazingly, by using its legs (which are well-endowed with blood vessels) to aid the process. Even then it has to constantly shuffle its eggs around in the nest to ensure that all receive sufficient heat, something picked up as a constant ‘clunking’ sound though a researcher’s microphone placed within a nest.

The book’s coverage is wide ranging to reflect the huge diversity in birds’ eggs and breeding behaviour but two species form a central thread running through the book and the author returns to these repeatedly. One is the domestic chicken Gallus gallus domesticus, the subject of intensive global research as a result of its commercial importance. Much of our understanding of how eggs are formed, the process of laying, embryo development and hatching come from this well-studied species. The second is the Common Guillemot Uria aalge, Tim Birkhead’s primary study species during his research career. This is a bird whose highly varied eggs attracted much early attention from collectors and has provoked interest among researchers ever since. The teaser as to why the Guillemot’s eggs are so strongly pointed is a recurring theme and is not resolved until near the end (and even then not fully). If you think you already know the answer, you may come away surprised.

The way that our knowledge and understanding has developed over time is also a recurring theme in the book. It is part of the story-telling approach; highlighting early insights and breakthroughs from long ago, as well as examples where people got things badly wrong. Early misunderstandings could be passed on unquestioningly from one authority to another, setting back knowledge of how things really worked for decades. We have come a long way in recent times but significant and sometimes surprising gaps in knowledge remain.

The book strays, forgivably, from its main subject in the final few pages and finishes on a poignant note, reflecting on the potential impacts of climate change on birds and the value of funding long-term research studies, a subject that he is better placed to comment on than most.

Ian Carter