Ontogeny of aerial righting and wing flapping in juvenile birds

Abstract

Mechanisms of aerial righting in juvenile Chukar Partridge (Alectoris chukar) were studied from hatching through 14 days-post-hatching (dph). Asymmetric movements of the wings were used from 1-8 dph to effect progressively more successful righting behaviour via body roll. Following 8 dph, wing motions transitioned to bilaterally symmetric flapping that yielded aerial righting via nose-down pitch, along with substantial increases in vertical force production during descent. Ontogenetically, the use of such wing motions to effect aerial righting precedes both symmetric flapping and a previously documented behaviour in chukar (i.e., wing-assisted incline running) hypothesized to be relevant to incipient flight evolution in birds. These findings highlight the importance of asymmetric wing activation and controlled aerial manoeuvres during bird development, and are potentially relevant to understanding the origins of avian flight.

Shifts in stability and control effectiveness during evolution of Paraves support aerial maneuvering hypotheses for flight origin

“…To explore parallel evolution and for calibration, we also constructed models of three pterosaurs, two bats, and two artificial test objects (sphere and weather vane) (Figure 2). Construction methods closely followed those of (Koehl et al, 2011; Evangelista et al, 2014b; Evangelista, 2013; Munk, 2011; Zeng, 2013). Solid models were developed in 95 Blender (The Blender Foundation, Amsterdam), closely referencing published photographs of fossils and reconstructions from the peer-reviewed literature and casts of Archaeopteryx to match long bone, axial skeleton, and body proportions.…”

“…For control effectiveness, we tested fixed static appendage movements previously identified as being aerodynamically effective (Evangelista et al, 2014b; Evangelista, 2013): asymmetric wing pronation and supination, wing tucking, symmetric wing protraction and retraction, and dorsoventral and lateral movements of the tail (Figure 3). The angular extent of each movement tested is shown on figure 3.…”

“…Under the test conditions, the aerodynamic coefficients of interest are reasonably constant with Reynolds number, Re = UL/v , where L here is the snout-vent length and v is the kinematic viscosity of air (Evangelista et al, 2014b; Evangelista, 2013). Early in the evolution of animal flight, organisms likely flew at moderate speeds and high angles of attack (Evangelista et al, 2014b; Dyke et al, 2013) where flows appear like bluff body turbulent flows (in which coefficients are largely independent of Re, for 10 3 < Re < 10 6 ).…”

“…While alternative postures have been considered (specifically in Microraptor ; Xu et al, 2003; Chatterjee and Templin, 2007; Davis, 2008; Alexander et al, 2010; Hone et al, 2010; Koehl et al, 2011; Habib et al, 2012; Hall et al, 2012; Evangelista et al, 2014; Dyke et al, 2013; including some now considered infeasible), the aim of this study was to examine maneuvering within several species rather than the posture of one, and the legs-back posture is seen in extant birds as well as supported for the fossils (Xu et al, 2004; Davis, 2008). For control effectiveness, we tested fixed static appendage movements previously identified as being aerodynamically effective (Evangelista et al, 2014; Evangelista, 2013): asymmetric wing pronation and supination, wing tucking, symmetric wing protraction and retraction, and dorsoventral and lateral movements of the tail (figure 2). The angular extent of each movement tested is shown on figure 2.…”

“…The angular extent of each movement tested is shown on figure 2. To avoid confusion, we present data for specimens as described with all appendages present; artificial manipulations (such as removal of tail and leg surfaces) were discussed in (Evangelista et al, 2014; Evangelista, 2013).

Figure 2. Appendage movements tested to determine control effectiveness.

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