The Eagle Owl

Given that the Eagle Owl Bubo bubo is one of the largest owls in the world and occurs in most of the Western Palearctic countries it comes as something of a surprise that this is the first book dedicated to it. However, Vincenzo Penteriani and María del Mar Delgado have now brought together everything that is known about the species from studies across its range, and not least from their own work spanning thirty years in Spain, Italy, France and Finland.

Having outlined the species and its many races from western Europe to eastern Siberia the authors give extensive details of distribution and population density in each country, including the UK. In some cases, these populations have been augmented through official and unofficial releases, and thanks to these projects the birds have returned to countries such as Denmark and Luxembourg where they had become extinct. After considerable declines in Europe in the last century due to the fall in rabbit populations, numbers are now increasing in countries such as Spain, France, the Netherlands and Belgium, yet declining in Finland, Switzerland and Russia. In many countries, the situation is simply unknown.

There is a chapter assessing the diet of Eagle Owls, and for those who thought they just ate rabbits and hedgehogs there is an amazing list of around 800 prey items recorded. The authors investigate interspecific interactions with other birds and describe the breeding year. Causes of mortality are explored, and being a huge bird Eagle Owls are frequently electrocuted on power lines, and sadly too many people persecute them as well. Eagle Owl territories are often difficult to locate so it is amazing to learn that in their studies the authors have found them breeding at high densities in south-west Spain with as many as 40 pairs per 100 sq km. This is a species that avoids dense forest and prefers relatively open country, and although they generally avoid living alongside humans there are some locations where the birds have moved into cities and can be found nesting on buildings. Often such situations exist because of the nearby presence of rubbish dumps and therefore larger rodents which can be preyed upon. The book covers all aspects of the species’ life from the breeding process, nest success, home range behaviour and post-breeding dispersal and there are also chapters on visual and vocal communication. In particular, the significance of white feather patches below the bill and on the breast in visual signalling is explored, revealing that the owls call more when their throat patch contrasts most with their surroundings.

There is a huge amount of detail in this book and it is thoroughly rigorous in its approach to reporting what is known. The text is quite dense on each page with few paragraphs, some of which last over last over 1000 words. That said, the authors have brought together a huge amount of information into one place, drawing on more than 1300 references, almost 60 of which they were heavily involved with. Perhaps one day Eagle Owls will become more of a feature of the UK’s avifauna. The evidence suggests that they were here thousands of years ago and perhaps the tiny population of escaped and released birds will spread. This book provides the background to the success of this enigmatic species in a world where factors are often loaded against them.