By Alexandre Roulin
Cambridge University Press, 2020
Hbk, 297pp; many photographs, colour illustrations and line-drawings
ISBN 978-1-107-16575-5; £39.99
First impressions are often reliable when it comes to books and a quick flick through the pages of this volume provided grounds for optimism. The text is well organised in short, manageable sections and the book is beautifully illustrated throughout by the artwork of Laurent Willenegger and many well-chosen colour photographs.
The structure of the book is unusual, with short sections of just a few pages for each topic, rounded off with a brief list of options for further reading. It has the feel of an undergraduate-level text book, reflecting the clarity of the text, the visual appeal of the layout and the way that the cosmopolitan Barn Owl Tyto alba is used as a case study to shed light on more widely applicable principles. The coverage is based mostly on research on Barn Owls in Europe but studies from North America and on related Tyto species, including the grass, masked and sooty owls, are referred to where relevant. Regional variation in Barn Owls and related species is well described, although no explanation is provided for an approach that splits the Tyto genus into 17 species across six continents.
As implied by the title, the book concentrates on aspects of ecology and physiology that can be linked to evolutionary pressures, both past and present. The author has an impressive track record of scientific research in this area and is especially interested in the adaptive significance of nestling behaviour and variations in plumage. There is a fascinating section on cooperation in nestlings. They apparently go to great lengths to negotiate peacefully (if not quietly) to try to establish which of them is most in need of the next prey item. They also feed each other and help to keep each other warm and free from parasites. Of course, harmony does not always prevail. Adults have been known to kill nestlings, while nestlings themselves can turn on each other if the need for food becomes critical. It seems that, as with humans, Barn Owls are capable of the very best and very worst of behaviours.
Plumage variation between the sexes and among different populations is dealt with in some detail, revealing a situation of bewildering complexity that is far from completely understood. Variations in background colour, spot size, and spot density all influence ecology and survival, and the author has spent many years attempting to disentangle the various mechanisms involved and their genetic basis.
If the book has a slight weakness, it is that (for an academic volume) references are not cited within the text. There were occasions when I wanted to check the original source for a statement but it was not always straightforward to locate it. To take an interesting example, one graph suggests that females with the smallest-diameter black feather spots have almost no chance of surviving their first year, in contrast to survival rates of over 60% for those with large spots. Can that really be true? It appears that it is, but it took a little time to track down the relevant paper.
Minor inconveniences aside, this is a thoroughly enjoyable and comprehensive introduction to the Barn Owl. It is one of a number of books on the Barn Owl but it will be the first one I turn to in future when seeking information about this bird’s lifestyle and ecology.