Barn Owls Evolution and Ecology – with Grass Owls, Masked Owls and Sooty Owls

Over the years, the genus Tyto has attracted a lot of attention from researchers and much of this has been fuelled by studies on the Barn Owl. Indeed, a quick check of my own library reveals that I already have no fewer than nine books on this species. So do we need another book on the subject? Actually, yes, because there are still many unanswered questions about this species, and in his book, Alexandre Roulin sets plenty of challenges for future researchers to tackle.

Roulin is Professor of Biology at the University of Lausanne in Switzerland and has been at the forefront of Barn Owl research since 1996. One of his particular areas of interest has been plumage polymorphism but he has also studied parent-offspring conflict and sibling competition. These subjects are well covered, but so too are conservation, parasites, predators, physiology, morphology, daily life, sexual behaviour, reproduction, parental care and demography.

Compared to other Barn Owl books I own, this one is more towards the academic end of the scale, but I was delighted that its style is engaging and approachable to anyone who is fascinated by owls and how they live. Rather than dense text, Roulin has chosen to create eleven chapters, each of which has many sub-sections. The result is a highly informative book that is easy to dip into for facts and attractively illustrated with art from Laurent Willenegger in addition to colour photographs.

Many little-known facts come to light in this book. For example that variation in the size of black feather spots can predict aspects of genetic quality, physiology and personality. Amazingly young females with the smallest black feather spots have a very small survival rate compared to those with larger spots. I was also fascinated by Roulin’s own studies of the 'sibling negotiation theory' that reveals how young Barn Owls communicate vocally to resolve conflicts peacefully. While we know quite a lot about the Barn Owl already, there is much less published about the other members of the Tyto genus (Grass, Masked and Sooty Owls). There are plenty of references to these scattered within the text. On the matter of references, these are given at the end of each chapter, although they are not cited within the text blocks.

The book does sound a few alarms. Disturbance by people is becoming a serious problem for most of the Tyto owls. Despite strong populations in some areas thanks to local conservation action, numbers elsewhere are indicating serious declines. Roulin wants more people to understand that these owls are efficient biological pest control agents – and people should know a single family of owls can devour between up to 7000 small mammals in a year!

Many questions remain and he poses these in each chapter. For example, do owls contract diseases by living in a dirty nest? Also, have they evolved an efficient immune system to combat endoparasites? It is also possible that Barn Owls from different populations may differ in their visual and hearing capacity because they prey upon different species requiring different hunting techniques. There is also scope for studying the daily food consumption of wild owls as most estimates have come from birds kept in captivity. Anyone lacking a subject for their PhD would benefit from reading Roulin’s suggestions for future research.

This is a well-organised book that delivers facts in a very approachable manner. It allows the reader to cherry-pick areas to read or simply work their way through the chapters. It was a delight to read.