Intra-specific variation in wing morphology and its impact on take-off performance in blue tits (Cyanistes caeruleus) during escape flights

Abstract

Diurnal and seasonal increases in body mass and seasonal reductions in wing area may compromise a bird's ability to escape, as less of the power available from the flight muscles can be used to accelerate and elevate the animal's centre of mass. Here, we investigated the effects of intra-specific variation in wing morphology on escape take-off performance in blue tits (Cyanistes caeruleus). Flights were recorded using synchronised high-speed video cameras and take-off performance was quantified as the sum of the rates of change of the kinetic and potential energies of the centre of mass. Individuals with a lower wing loading, WL (WL=body weight/wing area) had higher escape take-off performance, consistent with the increase in lift production expected from relatively larger wings. Unexpectedly, it was found that the total power available from the flight muscles (estimated using an aerodynamic analysis) was inversely related to WL. This could simply be because birds with a higher WL have relatively smaller flight muscles. Alternatively or additionally, variation in the aerodynamic load on the wing resulting from differences in wing morphology will affect the mechanical performance of the flight muscles via effects on the muscle's length trajectory. Consistent with this hypothesis is the observation that wing beat frequency and relative downstroke duration increase with decreasing WL; both are factors that are expected to increase muscle power output. Understanding how wing morphology influences take-off performance gives insight into the potential risks associated with feather loss and seasonal and diurnal fluctuations in body mass.

Species With Greater Aerial Maneuverability Have Higher Frequency of Collisions With Aircraft: A Comparative Study

“…However, we caution that this result although significant explained a low proportion of variability in bird strikes (∼11%). From the perspective of birds trying to avoid a collision by changing flight direction very quickly and sharply (Bernhardt et al, 2010) or trying to take-off quickly and at a sharp angle from the ground or perching position (Witter et al, 1994;Kullberg et al, 1996;Lind et al, 1999;McFarlane et al, 2016), this finding might seem counterintuitive. Yet, Santos et al (2016) also found a similar trend (i.e., positive association between bird collisions with cars and wing loading) relative to road kills.…”

“…Fourth, based on the fact that birds try to avoid collisions with aircraft by veering from their flight paths (Bernhardt et al, 2010), we hypothesized that species with morphological adaptations that enhance maneuverability would be at an advantage to engage in quick steering away (i.e., faster escape speed; Burns and Ydenberg, 2002;McFarlane et al, 2016) from an approaching vehicle to prevent a strike (Brown and Bomberger Brown, 2013;Santos et al, 2016). Two measures of wing morphology can be used as indices of maneuverability: (1) wing loading (i.e., ratio of body mass to wing area), which reflects the ability of a wing to turn relative to body mass (i.e., increasing with lower wing loadings; Lindhe Norberg, 2002); and (2) wing aspect ratio (i.e., ratio of wing span squared to wing area), which reflects the ability of a wing to quickly change direction (i.e., increasing with lower aspect ratios; Alexander, 2002).…”

Simulated moult reduces flight performance but overlap with breeding does not affect breeding success in a long‐distance migrant

“…This was supported by a number of studies in laboratory conditions that quantified the effects of moult on flight performance (Chai, ; Swaddle & Witter, ; Swaddle et al., ; Williams & Swaddle, ), suggesting that wing gaps could be detrimental to the individual, for example, in terms of predation pressure (Lind, Jakobsson, & Kullberg, ; Swaddle & Witter, ). Curiously, this ends up generating a segregation: because fitness should be investigated in field conditions while flight dynamics studies require a controlled environment, fitness costs of moult‐breeding overlap have been looked at in the field assuming a locomotion cost (Table ; see also Echeverry‐Galvis & Hau, for an exception), and effects of moult on locomotion have been quantified in laboratory settings (see McFarlane, Altringham, & Askew, for a field example) assuming a fitness cost to the individual bird, outside the context of moult‐breeding overlap.…”

Physiological maturity at a critical life‐history transition and flight ability at fledging

“…One possible explanation for this may be the optimization of wing loading (body mass/wing area). Wing loading has been shown to play an important role in escape flight in adult birds (Burns & Ydenberg ; McFarlane, Altringham & Askew ) and relates to flight performance in fledglings (Verspoor et al . ; Chin et al .…”

“…One possible explanation for this may be the optimization of wing loading (body mass/wing area). Wing loading has been shown to play an important role in escape flight in adult birds (Burns & Ydenberg 2002;McFarlane, Altringham & Askew 2016) and relates to flight performance in fledglings Chin et al 2009). Experimental manipulations using mass weights and feather clipping have already demonstrated that nestlings modify their somatic development in order to maintain targeted wing loading values at fledging (Wright, Markman & Denney 2006).…”