Feathers of European Owls fills many gaps in current knowledge of owl feathers. The author not only describes the identification of feathers of the European owl species, but also presents relationships between feather morphology and the behaviour and ecology of this group of birds. These findings are largely based on the Author’s original research, and his extensive collection of feathers.

Contents

Obituary 7
From the publishers 9
Introduction 11

Part A – Description of owl feathers 13
Basic information on feathers 13
Types of feather 13
Wings 18
The tail 21
Specifc features of owl feathers 23
Primaries 23
Secondaries 25
Rectrices (tail feathers) 26
Other smaller feathers 27
Abnormalities in feather numbers 32
Owl feather dimorphism 34

Part B – The ecology of owls and their plumage 39
B1. Analysis of owl silhouettes in flight 39
B2. Wing-loading 44
B3. Feather colouration and pattern 48
The optimised distribution of pigment in the plumage of owls 51
The optimised distribution of pigment in feathers 52
The species-related variability in colouration pattern 53
Aberrations in the colouring of owl plumage 58
Albinism and leucism 58
Melanism 61
B4. The silent flight mechanisms in owls 62
The diversity of silent flight mechanisms in European owl species 70
The auditory abilities of owls 70
Daily activity and type of diet 73
Audiles, generalists and visualisers 74
The silent flight mechanisms in different hunting strategies 77
Silent flight and owls’ aviation capabilities 81
Ecological isolation between owl species 83
B5. Moulting strategies 87
The effect of moulting on owls’ flying abilities 89
The sequence of moulting 90
The frequency of replacement of individual feathers 92
Moult phenology in relation to breeding and migration 93
How long does moulting a generation of feathers take? 95
Feather grow rates 96
B6. Why owls have developed a diastataxic wing type? 98
B7. Stress bars 104
B8. The bioindication of environmental pollution using owl feathers 110

Part C – Species review 113
Western Barn Owl Tyto alba 113
Eurasian Scops Owl Otus scops 116
Eurasian Eagle-Owl Bubo bubo 117
Snowy Owl Bubo scandiacus 119
Northern Hawk-Owl Surnia ulula 121
Eurasian Pygmy Owl Glaucidium passerinum 124
Little Owl Athene noctua 125
Great Grey Owl Strix nebulosa 127
Ural Owl Strix uralensis 131
Tawny Owl Strix aluco 133
Long-eared Owl Asio otus 135
Short-eared owl Asio ?ammeus 137
Marsh Owl Asio capensis 139
Boreal Owl (Tengmalm’s Owl) Aegolius funereus 141

Part D – Identifcation of feathers from among the European species of owl 143
Variety in owl feathers 144
A feather identifcation procedure 144
Reasons for the presence of feathers 145
Assigning species to groups 145
Large owls 146
Medium-sized owls 155
Small owls 165

Ending 171
Acknowledgments 171

References 173
Appendices 183