Distribution of the characteristics of barbs and barbules on barn owl wing feathers

Abstract

Owls are known for the development of a silent flight. One conspicuous specialization of owl wings that has been implied in noise reduction and that has been demonstrated to change the aerodynamic behavior of the wing is a soft dorsal wing surface. The soft surface is a result of changes in the shape of feather barbs and barbules in owls compared with other bird species. We hypothesized that as the aerodynamic characteristics of a wing change along its chordwise and spanwise direction, so may the shape of the barbs and barbules. Therefore, we examined in detail the shapes of the barbs and barbules in chordwise and spanwise directions. The results showed changes in the shapes of barbs and barbules at the anterior and distal parts of the wing, but not at more posterior parts. The increased density of hook radiates at the distalmost wing position could serve to stiffen that vane part that is subject to the highest forces. The change of pennulum length in the anterior part of the wing and the uniformity further back could mean that a soft surface may be especially important in regions where flow separation may occur.

Features of the architectonics of the microstructure of the primary remex of Owls (Strigiformes) due to the specifics of the flight

“…8, F; Fig. 9, f, F, G), also known as fringes [17,19,22], of the inner vane, well expressed in all species of Strigiformes studied by us. At the same time, the degree of the cleavage of the edge of the inner vane in N. scandiaca is less expressed than the other species studied by us, that which is consistent with the results of our previous studies [25,26,29,30].…”

“…Due to the tight adjoining highly elongated barbules to each other and to the apical portion of the ramus, the distinctive "bunch", also known as a fringe [17,19,22], is formed (Fig. 8, E; Fig.…”

“…At present, the biology of the Strigiformes has been studied in some detail [1][2][3][4][5][6][7][8][9][10][11][12]. Nevertheless, in modern works that provide detailed descriptions of distinctive species-specific morphological features in the body structure and plumage of the Strigiformes [13][14][15], including an exhaustive description of the main aerodynamically advantageous macro-morphological characteristics of the contour feather of individual representatives of the Strigiformes [16][17][18][19][20][21][22], there is almost no information about microstructural features of the feather cover of the Strigiformes.…”

Genomic Evidence for Sensorial Adaptations to a Nocturnal Predatory Lifestyle in Owls

“…The feathers of owls have a special noise absorption structure that allows them to fly silently while hunting, and this feature has been studied morphologically and acoustically ( Kopania 2016 ; Sagar et al. 2017 ; Weger and Wagner 2017) . However, the genetic correlates of this adaptation in owls remain unclear.…”

Flow Features of the Near Wake of the Australian Boobook Owl (Ninox boobook) During Flapping Flight Suggest an Aerodynamic Mechanism of Sound Suppression for Stealthy Flight

“…Relative to the role of feathers ( Wagner et al. 2017 ; Weger and Wagner 2017 ), investigations of the wake characteristics, and their relation to quantities like pressure that influence noise generation, are sparse. In particular, wake measurements of freely flying owls that account for all of the aforementioned feather features, along with flying behavior, are lacking.…”