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Morphometric characterisation of wing feathers of the barn owl Tyto alba pratincola and the pigeon Columba livia.

Bachmann T, Klän S, Baumgartner W, Klaas M, Schröder W, Wagner H - Front. Zool. (2007)

Bottom Line: Even though there is some information available on the mechanisms that lead to a reduction of noise emission, neither the morphological basis, nor the biological mechanisms of the owl's silent flight are known.We also present a quantitative description of several characteristic features of barn owl feathers, e.g., the serrations at the leading edge of the wing, the fringes at the edges of each feather, and the velvet-like dorsal surface.The quantitative description of the feathers and the specific structures of owl feathers can be used as a model for the construction of a biomimetic airplane wing or, in general, as a source for noise-reducing applications on any surfaces subjected to flow fields.

View Article: PubMed Central - HTML - PubMed

Affiliation: RWTH Aachen University, Institute of Biology II, Aachen, Germany. bachmann@bio2.rwth-aachen.de.

ABSTRACT

Background: Owls are known for their silent flight. Even though there is some information available on the mechanisms that lead to a reduction of noise emission, neither the morphological basis, nor the biological mechanisms of the owl's silent flight are known. Therefore, we have initiated a systematic analysis of wing morphology in both a specialist, the barn owl, and a generalist, the pigeon. This report presents a comparison between the feathers of the barn owl and the pigeon and emphasise the specific characteristics of the owl's feathers on macroscopic and microscopic level. An understanding of the features and mechanisms underlying this silent flight might eventually be employed for aerodynamic purposes and lead to a new wing design in modern aircrafts.

Results: A variety of different feathers (six remiges and six coverts), taken from several specimen in either species, were investigated. Quantitative analysis of digital images and scanning electron microscopy were used for a morphometric characterisation. Although both species have comparable body weights, barn owl feathers were in general larger than pigeon feathers. For both species, the depth and the area of the outer vanes of the remiges were typically smaller than those of the inner vanes. This difference was more pronounced in the barn owl than in the pigeon. Owl feathers also had lesser radiates, longer pennula, and were more translucent than pigeon feathers. The two species achieved smooth edges and regular surfaces of the vanes by different construction principles: while the angles of attachment to the rachis and the length of the barbs was nearly constant for the barn owl, these parameters varied in the pigeon. We also present a quantitative description of several characteristic features of barn owl feathers, e.g., the serrations at the leading edge of the wing, the fringes at the edges of each feather, and the velvet-like dorsal surface.

Conclusion: The quantitative description of the feathers and the specific structures of owl feathers can be used as a model for the construction of a biomimetic airplane wing or, in general, as a source for noise-reducing applications on any surfaces subjected to flow fields.

No MeSH data available.


Asymmetry of barn owl and pigeon wing feathers. Asymmetry index of depth. Presents the asymmetry of the depth in the remiges (A, B) and coverts (C, D) in the barn owl (A, C) and the pigeon (B, D). The colours indicate different feathers. Their position is presented at the wing.
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Figure 3: Asymmetry of barn owl and pigeon wing feathers. Asymmetry index of depth. Presents the asymmetry of the depth in the remiges (A, B) and coverts (C, D) in the barn owl (A, C) and the pigeon (B, D). The colours indicate different feathers. Their position is presented at the wing.

Mentions: The depth of the vane as a function of its length was measured and the mean value was calculated. For all examined feathers (except for the secondary coverts in the pigeon), the outer vane was smaller than the inner vane (Fig. 2). The asymmetry index AId, introduced in the Methods section (Eqn. 1), revealed two morphometric characteristics (Fig. 3): On the one hand, the asymmetry in the pigeon's remige was smaller and, on the other hand, showed a much higher variation along the length of the feather compared to the barn owl. The mean asymmetry of the pigeon's remiges decreased from lateral to medial (p10, AId = -0.61; p1 AId = -0.23; s8, AId = -0.1), whereas the asymmetry of the barn owl's remiges changed only little (p10, AId = -0.66; p1, AId = -0.44; s8, AId = -0.42) (for position of the feathers see Fig. 1A).


Morphometric characterisation of wing feathers of the barn owl Tyto alba pratincola and the pigeon Columba livia.

Bachmann T, Klän S, Baumgartner W, Klaas M, Schröder W, Wagner H - Front. Zool. (2007)

Asymmetry of barn owl and pigeon wing feathers. Asymmetry index of depth. Presents the asymmetry of the depth in the remiges (A, B) and coverts (C, D) in the barn owl (A, C) and the pigeon (B, D). The colours indicate different feathers. Their position is presented at the wing.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211483&req=5

Figure 3: Asymmetry of barn owl and pigeon wing feathers. Asymmetry index of depth. Presents the asymmetry of the depth in the remiges (A, B) and coverts (C, D) in the barn owl (A, C) and the pigeon (B, D). The colours indicate different feathers. Their position is presented at the wing.
Mentions: The depth of the vane as a function of its length was measured and the mean value was calculated. For all examined feathers (except for the secondary coverts in the pigeon), the outer vane was smaller than the inner vane (Fig. 2). The asymmetry index AId, introduced in the Methods section (Eqn. 1), revealed two morphometric characteristics (Fig. 3): On the one hand, the asymmetry in the pigeon's remige was smaller and, on the other hand, showed a much higher variation along the length of the feather compared to the barn owl. The mean asymmetry of the pigeon's remiges decreased from lateral to medial (p10, AId = -0.61; p1 AId = -0.23; s8, AId = -0.1), whereas the asymmetry of the barn owl's remiges changed only little (p10, AId = -0.66; p1, AId = -0.44; s8, AId = -0.42) (for position of the feathers see Fig. 1A).

Bottom Line: Even though there is some information available on the mechanisms that lead to a reduction of noise emission, neither the morphological basis, nor the biological mechanisms of the owl's silent flight are known.We also present a quantitative description of several characteristic features of barn owl feathers, e.g., the serrations at the leading edge of the wing, the fringes at the edges of each feather, and the velvet-like dorsal surface.The quantitative description of the feathers and the specific structures of owl feathers can be used as a model for the construction of a biomimetic airplane wing or, in general, as a source for noise-reducing applications on any surfaces subjected to flow fields.

View Article: PubMed Central - HTML - PubMed

Affiliation: RWTH Aachen University, Institute of Biology II, Aachen, Germany. bachmann@bio2.rwth-aachen.de.

ABSTRACT

Background: Owls are known for their silent flight. Even though there is some information available on the mechanisms that lead to a reduction of noise emission, neither the morphological basis, nor the biological mechanisms of the owl's silent flight are known. Therefore, we have initiated a systematic analysis of wing morphology in both a specialist, the barn owl, and a generalist, the pigeon. This report presents a comparison between the feathers of the barn owl and the pigeon and emphasise the specific characteristics of the owl's feathers on macroscopic and microscopic level. An understanding of the features and mechanisms underlying this silent flight might eventually be employed for aerodynamic purposes and lead to a new wing design in modern aircrafts.

Results: A variety of different feathers (six remiges and six coverts), taken from several specimen in either species, were investigated. Quantitative analysis of digital images and scanning electron microscopy were used for a morphometric characterisation. Although both species have comparable body weights, barn owl feathers were in general larger than pigeon feathers. For both species, the depth and the area of the outer vanes of the remiges were typically smaller than those of the inner vanes. This difference was more pronounced in the barn owl than in the pigeon. Owl feathers also had lesser radiates, longer pennula, and were more translucent than pigeon feathers. The two species achieved smooth edges and regular surfaces of the vanes by different construction principles: while the angles of attachment to the rachis and the length of the barbs was nearly constant for the barn owl, these parameters varied in the pigeon. We also present a quantitative description of several characteristic features of barn owl feathers, e.g., the serrations at the leading edge of the wing, the fringes at the edges of each feather, and the velvet-like dorsal surface.

Conclusion: The quantitative description of the feathers and the specific structures of owl feathers can be used as a model for the construction of a biomimetic airplane wing or, in general, as a source for noise-reducing applications on any surfaces subjected to flow fields.

No MeSH data available.