{"id":{"repo_id":"aachen","oai_identifier":"oai:publications.rwth-aachen.de:51750"},"canonical_url":"https://search.dev.ndltd.org/etd/aachen/oai:publications.rwth-aachen.de:51750","repository":{"repo_id":"aachen","name":"RWTH Aachen University","base_url":"https://publications.rwth-aachen.de/oai2d"},"display":{"title":"Anatomical, morphometrical and biomechanical studies of barn owls' and pigeons' wings","abstract":"Wings and feathers of barn owls (Tyto alba) were investigated with anatomical, morphometrical and biomechanical methods in order to specify noise reduction and noise suppressing structures evolved by the owl. Pigeons (Columba livia) with a similar body weight were taken as a reference species. Barn owls' wings are 2.5 times larger in area size than wings of pigeons, resulting in a much lower wing loading. Furthermore, barn owls' wings are characterised by a high camber and a high thickness in anterior proximal wing regions and by a low camber and a low thickness in distal and posterior proximal wing regions. Such a wing configuration enables the barn owl to fly slowly, which in turn might reduce flight noise. Pigeons' wings are smaller, less cambered and show a different thickness distribution. Since their wings do not produce as much lift as wings of the barn owl, pigeons have to beat their wings at high frequencies in order to fly slowly, e.g. during take-off. In general, pigeons beat their wings more often than barn owls to produce more lift. The increased wing beat frequency is also reflected by the increased amount of muscle mass and the appearance of the supporting bones. Barn owls' wings are equipped with several surface and edge modifications that are responsible for either flow control or noise suppression or both. A new three-dimensional measuring method was established in order to reconstruct and investigate the filigree structures with high spatial resolution. Bending and shape of the serrations of the barn owl's 10^{ext{th}} primary remex was found to be more or less constant throughout the vane. Only length and tip shape differences were found that might be due to wearing effects or different angles of attack of the wing tip during flapping flight. Functionally, serrations might act as turbulence generators. Each feather of the wing is covered with a velvet-like dorsal surface formed by elongations of the hook radiates, the pennula. The structure of the pennula differed between covered and uncovered feather areas. In covered areas, the porosity of the pennula-structure was high and the pennula formed a friction reductive surface. The surface that is subjected to the air flow was characterised by a brush-like shape. The pennula tips ended in the air flow. At the same time the porosity was lower. Such a structure in combination with the wing geometry of barn owls stabilises the air flow, especially at low flight speed. Finally, the edges of the inner vanes of all flight feathers were fringed. On the one hand, fringes might merge the different fast air flows of the upper and lower wing side at the trailing edge of the wing, on the other hand, they might fuse superjacent vanes by gliding between the grooves formed by the ventral barb shafts. Thereby, a smooth lower wing surface might be formed without sharp and thus noisy edges. Biomechanical measurements with two independent methods (two-point bending tests and nanoindentation tests) were performed to determine the Young’s modulus of barn owls' and pigeons' feather keratin. While barn owls' feather keratin has a Young’s modulus of 6.6 GPa, the Young's modulus of pigeons' keratin is 7.5 GPa and thus by 12% higher. However, this difference could not explain the different bending behaviours of feathers of the two species. The geometry of the shafts had a large influence as well, which is expressed by several adaptations of the shaft's cortex. The results of this thesis may now be used for follow-up analysis of the mechanisms underlying noise reduction in a more veridical way.","abstract_html":"Wings and feathers of barn owls (Tyto alba) were investigated with anatomical, morphometrical and biomechanical methods in order to specify noise reduction and noise suppressing structures evolved by the owl. Pigeons (Columba livia) with a similar body weight were taken as a reference species. Barn owls' wings are 2.5 times larger in area size than wings of pigeons, resulting in a much lower wing loading. Furthermore, barn owls' wings are characterised by a high camber and a high thickness in anterior proximal wing regions and by a low camber and a low thickness in distal and posterior proximal wing regions. Such a wing configuration enables the barn owl to fly slowly, which in turn might reduce flight noise. Pigeons' wings are smaller, less cambered and show a different thickness distribution. Since their wings do not produce as much lift as wings of the barn owl, pigeons have to beat their wings at high frequencies in order to fly slowly, e.g. during take-off. In general, pigeons beat their wings more often than barn owls to produce more lift. The increased wing beat frequency is also reflected by the increased amount of muscle mass and the appearance of the supporting bones. Barn owls' wings are equipped with several surface and edge modifications that are responsible for either flow control or noise suppression or both. A new three-dimensional measuring method was established in order to reconstruct and investigate the filigree structures with high spatial resolution. Bending and shape of the serrations of the barn owl's 10^{ext{th}} primary remex was found to be more or less constant throughout the vane. Only length and tip shape differences were found that might be due to wearing effects or different angles of attack of the wing tip during flapping flight. Functionally, serrations might act as turbulence generators. Each feather of the wing is covered with a velvet-like dorsal surface formed by elongations of the hook radiates, the pennula. The structure of the pennula differed between covered and uncovered feather areas. In covered areas, the porosity of the pennula-structure was high and the pennula formed a friction reductive surface. The surface that is subjected to the air flow was characterised by a brush-like shape. The pennula tips ended in the air flow. At the same time the porosity was lower. Such a structure in combination with the wing geometry of barn owls stabilises the air flow, especially at low flight speed. Finally, the edges of the inner vanes of all flight feathers were fringed. On the one hand, fringes might merge the different fast air flows of the upper and lower wing side at the trailing edge of the wing, on the other hand, they might fuse superjacent vanes by gliding between the grooves formed by the ventral barb shafts. Thereby, a smooth lower wing surface might be formed without sharp and thus noisy edges. Biomechanical measurements with two independent methods (two-point bending tests and nanoindentation tests) were performed to determine the Young’s modulus of barn owls' and pigeons' feather keratin. While barn owls' feather keratin has a Young’s modulus of 6.6 GPa, the Young's modulus of pigeons' keratin is 7.5 GPa and thus by 12% higher. However, this difference could not explain the different bending behaviours of feathers of the two species. The geometry of the shafts had a large influence as well, which is expressed by several adaptations of the shaft's cortex. The results of this thesis may now be used for follow-up analysis of the mechanisms underlying noise reduction in a more veridical way.","abstract_has_math":false,"creators":["Bachmann, Thomas Willem"],"institution":"Publikationsserver der RWTH Aachen University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Wagner, Hermann"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2010,"date_issued":"2010","date_published":"2010","updated_at":"2026-07-30T19:40:42Z","subjects":["info:eu-repo/classification/ddc/590","Bionik","Vogelflug","Biomechanik","Funktionelle Anatomie","Schleiereule","Haustaube","Aerodynamik","Tiere (Zoologie)","biomimetic","bird flight","barn owl","pigeon","anatomy"],"languages":["eng"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-114008%22"],"render_values":[{"text":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-114008%22","href":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-114008%22","code":true}]}]},"links":{"outbound_url":"https://publications.rwth-aachen.de/record/51750","outbound_label":"Repository record","outbound_source":"dc:identifier"},"source_record":{"url":"https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A51750","prefix":"oai_dc"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Wagner, Hermann"]},{"key":"dc:creator","label":"Author","values":["Bachmann, Thomas Willem"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:coverage","label":"Dc Coverage","values":["DE"]},{"key":"dc:date","label":"Dc Date","values":["2010"]},{"key":"dc:publisher","label":"Institution","values":["Publikationsserver der RWTH Aachen University"]},{"key":"dc:relation","label":"Dc Relation","values":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-32516"]},{"key":"dc:type","label":"Dc Type","values":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["info:eu-repo/classification/ddc/590","Bionik","Vogelflug","Biomechanik","Funktionelle Anatomie","Schleiereule","Haustaube","Aerodynamik","Tiere (Zoologie)","biomimetic","bird flight","barn owl","pigeon","anatomy"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/record/51750","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-114008%22"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Wings and feathers of barn owls (Tyto alba) were investigated with anatomical, morphometrical and biomechanical methods in order to specify noise reduction and noise suppressing structures evolved by the owl. Pigeons (Columba livia) with a similar body weight were taken as a reference species. Barn owls' wings are 2.5 times larger in area size than wings of pigeons, resulting in a much lower wing loading. Furthermore, barn owls' wings are characterised by a high camber and a high thickness in anterior proximal wing regions and by a low camber and a low thickness in distal and posterior proximal wing regions. Such a wing configuration enables the barn owl to fly slowly, which in turn might reduce flight noise. Pigeons' wings are smaller, less cambered and show a different thickness distribution. Since their wings do not produce as much lift as wings of the barn owl, pigeons have to beat their wings at high frequencies in order to fly slowly, e.g. during take-off. In general, pigeons beat their wings more often than barn owls to produce more lift. The increased wing beat frequency is also reflected by the increased amount of muscle mass and the appearance of the supporting bones. Barn owls' wings are equipped with several surface and edge modifications that are responsible for either flow control or noise suppression or both. A new three-dimensional measuring method was established in order to reconstruct and investigate the filigree structures with high spatial resolution. Bending and shape of the serrations of the barn owl's 10^{ext{th}} primary remex was found to be more or less constant throughout the vane. Only length and tip shape differences were found that might be due to wearing effects or different angles of attack of the wing tip during flapping flight. Functionally, serrations might act as turbulence generators. Each feather of the wing is covered with a velvet-like dorsal surface formed by elongations of the hook radiates, the pennula. The structure of the pennula differed between covered and uncovered feather areas. In covered areas, the porosity of the pennula-structure was high and the pennula formed a friction reductive surface. The surface that is subjected to the air flow was characterised by a brush-like shape. The pennula tips ended in the air flow. At the same time the porosity was lower. Such a structure in combination with the wing geometry of barn owls stabilises the air flow, especially at low flight speed. Finally, the edges of the inner vanes of all flight feathers were fringed. On the one hand, fringes might merge the different fast air flows of the upper and lower wing side at the trailing edge of the wing, on the other hand, they might fuse superjacent vanes by gliding between the grooves formed by the ventral barb shafts. Thereby, a smooth lower wing surface might be formed without sharp and thus noisy edges. Biomechanical measurements with two independent methods (two-point bending tests and nanoindentation tests) were performed to determine the Young’s modulus of barn owls' and pigeons' feather keratin. While barn owls' feather keratin has a Young’s modulus of 6.6 GPa, the Young's modulus of pigeons' keratin is 7.5 GPa and thus by 12% higher. However, this difference could not explain the different bending behaviours of feathers of the two species. The geometry of the shafts had a large influence as well, which is expressed by several adaptations of the shaft's cortex. The results of this thesis may now be used for follow-up analysis of the mechanisms underlying noise reduction in a more veridical way."]},{"key":"dc:source","label":"Dc Source","values":["Aachen : Publikationsserver der RWTH Aachen University II, 91 Bl. : Ill., graph. Darst. (2010). = Aachen, Techn. Hochsch., Diss., 2010"]},{"key":"dc:title","label":"Title","values":["Anatomical, morphometrical and biomechanical studies of barn owls' and pigeons' wings"]}]}],"canonical_facts":{"dc:contributor":["Wagner, Hermann"],"dc:coverage":["DE"],"dc:creator":["Bachmann, Thomas Willem"],"dc:date":["2010"],"dc:description":["Wings and feathers of barn owls (Tyto alba) were investigated with anatomical, morphometrical and biomechanical methods in order to specify noise reduction and noise suppressing structures evolved by the owl. Pigeons (Columba livia) with a similar body weight were taken as a reference species. Barn owls' wings are 2.5 times larger in area size than wings of pigeons, resulting in a much lower wing loading. Furthermore, barn owls' wings are characterised by a high camber and a high thickness in anterior proximal wing regions and by a low camber and a low thickness in distal and posterior proximal wing regions. Such a wing configuration enables the barn owl to fly slowly, which in turn might reduce flight noise. Pigeons' wings are smaller, less cambered and show a different thickness distribution. Since their wings do not produce as much lift as wings of the barn owl, pigeons have to beat their wings at high frequencies in order to fly slowly, e.g. during take-off. In general, pigeons beat their wings more often than barn owls to produce more lift. The increased wing beat frequency is also reflected by the increased amount of muscle mass and the appearance of the supporting bones. Barn owls' wings are equipped with several surface and edge modifications that are responsible for either flow control or noise suppression or both. A new three-dimensional measuring method was established in order to reconstruct and investigate the filigree structures with high spatial resolution. Bending and shape of the serrations of the barn owl's 10^{ext{th}} primary remex was found to be more or less constant throughout the vane. Only length and tip shape differences were found that might be due to wearing effects or different angles of attack of the wing tip during flapping flight. Functionally, serrations might act as turbulence generators. Each feather of the wing is covered with a velvet-like dorsal surface formed by elongations of the hook radiates, the pennula. The structure of the pennula differed between covered and uncovered feather areas. In covered areas, the porosity of the pennula-structure was high and the pennula formed a friction reductive surface. The surface that is subjected to the air flow was characterised by a brush-like shape. The pennula tips ended in the air flow. At the same time the porosity was lower. Such a structure in combination with the wing geometry of barn owls stabilises the air flow, especially at low flight speed. Finally, the edges of the inner vanes of all flight feathers were fringed. On the one hand, fringes might merge the different fast air flows of the upper and lower wing side at the trailing edge of the wing, on the other hand, they might fuse superjacent vanes by gliding between the grooves formed by the ventral barb shafts. Thereby, a smooth lower wing surface might be formed without sharp and thus noisy edges. Biomechanical measurements with two independent methods (two-point bending tests and nanoindentation tests) were performed to determine the Young’s modulus of barn owls' and pigeons' feather keratin. While barn owls' feather keratin has a Young’s modulus of 6.6 GPa, the Young's modulus of pigeons' keratin is 7.5 GPa and thus by 12% higher. However, this difference could not explain the different bending behaviours of feathers of the two species. The geometry of the shafts had a large influence as well, which is expressed by several adaptations of the shaft's cortex. The results of this thesis may now be used for follow-up analysis of the mechanisms underlying noise reduction in a more veridical way."],"dc:identifier":["https://publications.rwth-aachen.de/record/51750","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-114008%22"],"dc:language":["eng"],"dc:publisher":["Publikationsserver der RWTH Aachen University"],"dc:relation":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-32516"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:source":["Aachen : Publikationsserver der RWTH Aachen University II, 91 Bl. : Ill., graph. Darst. (2010). = Aachen, Techn. Hochsch., Diss., 2010"],"dc:subject":["info:eu-repo/classification/ddc/590","Bionik","Vogelflug","Biomechanik","Funktionelle Anatomie","Schleiereule","Haustaube","Aerodynamik","Tiere (Zoologie)","biomimetic","bird flight","barn owl","pigeon","anatomy"],"dc:title":["Anatomical, morphometrical and biomechanical studies of barn owls' and pigeons' wings"],"dc:type":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]},"updated_at":"2026-07-30T19:40:42Z"}