Empirical Estimates of Body Drag of Large Waterfowl and Raptors

Pennycuick, Colin J; Obrecht, Holliday H.; Fuller, Mark R.

doi:10.1242/jeb.135.1.253

Cited by 86 publications

(12 citation statements)

References 6 publications

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“…The bird’s aerodynamic power output implies a tangential aerodynamic thrust force T = P ⁄ V , where V is the bird’s airspeed neglecting any induced velocity component. We model the opposing aerodynamic drag as where ρ = 1.23 kg m −3 is air density and where S b = 0.00813 m 2/3 is an empirical scaling relationship 47 modelling body frontal area S b as a function of body mass m . Here b is wingspan and S is wing area, both of which are assumed to be maximal throughout the manoeuvre (Table 1 ).…”

Section: Methodsmentioning

confidence: 99%

Optimization of avian perching manoeuvres

KleinHeerenbrink

France

Brighton

et al. 2022

Nature

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Perching at speed is among the most demanding flight behaviours that birds perform1,2 and is beyond the capability of most autonomous vehicles. Smaller birds may touch down by hovering3–8, but larger birds typically swoop up to perch1,2—presumably because the adverse scaling of their power margin prohibits hovering9 and because swooping upwards transfers kinetic to potential energy before collision1,2,10. Perching demands precise control of velocity and pose11–14, particularly in larger birds for which scale effects make collisions especially hazardous6,15. However, whereas cruising behaviours such as migration and commuting typically minimize the cost of transport or time of flight16, the optimization of such unsteady flight manoeuvres remains largely unexplored7,17. Here we show that the swooping trajectories of perching Harris’ hawks (Parabuteo unicinctus) minimize neither time nor energy alone, but rather minimize the distance flown after stalling. By combining motion capture data from 1,576 flights with flight dynamics modelling, we find that the birds’ choice of where to transition from powered dive to unpowered climb minimizes the distance over which high lift coefficients are required. Time and energy are therefore invested to provide the control authority needed to glide safely to the perch, rather than being minimized directly as in technical implementations of autonomous perching under nonlinear feedback control12 and deep reinforcement learning18,19. Naive birds learn this behaviour on the fly, so our findings suggest a heuristic principle that could guide reinforcement learning of autonomous perching.

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Section: Methodsmentioning

confidence: 99%

Optimization of avian perching manoeuvres

KleinHeerenbrink

France

Brighton

et al. 2022

Nature

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“…Every reduction in drag or increase in lift can therefore improve the flight efficiency of a bird. Larger wing surfaces, for example, can increase lift (Tobalske 2007), while a streamlined body reduces drag (Pennycuick et al 1988). Recent studies have suggested that wing surface heating under solar radiation could affect the lift-to-drag ratio of a flying bird and that this effect would be stronger in hotter, dark-winged birds (Hassanalian et al 2017, 2018a, 2018b, Rogalla et al 2019.…”

Section: Thermal Effects Of Wing Coloration On Flight Performancementioning

confidence: 99%

Thermal effects of plumage coloration

Rogalla

Shawkey

D’Alba

2022

Ibis

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Plumage coloration can have substantial effects on a bird's energy budget. This is because different colours reflect and absorb light differently, affecting the heat loads acquired from solar radiation. We examine the thermal effects of feather coloration on solar heat gain and flight performance and discuss the potential role of plumage colour on a bird's energy budget. Early investigations of the effects of plumage colour on thermoregulation revealed complex interactions between environmental conditions and physical properties of the plumage that may have led to diverse behavioural and physiological adaptations of birds to their thermal environment. While darker feather surfaces absorb more light, and heat more, than light‐coloured surfaces under exposure to the sun, this relationship is not always straightforward when considering heat transfer to the skin. Heat transfer through plumage varies depending on multiple factors, such as feather density and transmission of light. For instance, higher transmissivity of light‐coloured plumage can increase heat loads reaching skin level, while conduction and convection transfer heat from the surface of dark feathers to the skin. Solar heating can affect the metabolic costs of maintaining a constant body temperature, and depending on environmental conditions, colours can have either a positive or negative effect on a bird's energy budget. More specifically, solar heating can be advantageous in the cold but may increase the energetic costs associated with thermoregulation when ambient temperature is high. More recent studies have further suggested that the thermal properties of feather coloration might reduce the energetic costs of flight. This is because surface heating can affect the ratio between lift and drag on a wing. As concluding remarks, we provide future directions for new lines of research that will aid in improving our understanding of the thermal effects of feather coloration on a bird's energy budget, which can potentially explain factors driving colour evolution and distribution patterns in birds.

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“…This depends on the morphology of the bird and the Reynolds number Re according to with S b and FR t are respectively the frontal area of the body and the fitness ratio of the bird, and both of them can be estimated from other allometric formulas i.e. [20, 21]. The Reynolds number is calculated with the reference length of the mean aerodynamic chord , with µ being the dynamic viscosity.…”

Section: Dynamical Model Of Bird Flightmentioning

confidence: 99%

“…with S b and FR t are respectively the frontal area of the body and the fitness ratio of the bird, and both of them can be estimated from other allometric formulas i.e. [20,21].…”

Section: Drag Production By Body and Wingmentioning

confidence: 99%

On the role of tail in stability and energetic cost of bird flapping flight

Ducci

Vitucci

Chatelain

et al. 2022

Preprint

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Migratory birds travel over impressively long distances. Consequently, they have to adopt flight regimes being both efficient - in order to spare their metabolic resources - and robust to perturbations. This paper investigates the relationship between both aspects, i.e. mechanical performance and stability in flapping flight of migratory birds. Relying on a poly-articulated wing morphing model and a tail-like surface, several families of steady flight regime have been identified and analyzed. These families differ by their wing kinematics and tail opening. A systematic parametric search analysis has been carried out, in order to evaluate power consumption and cost of transport. A framework tailored for assessing limit cycles, namely Floquet theory, is used to numerically study flight stability. Our results show that under certain conditions, an inherent passive stability of steady and level flight can be achieved. In particular, we find that progressively opening the tail leads to passively stable flight regimes. Within these passively stable regimes, the tail can produce either upward or downward lift. However, these configurations entail an increase of cost of transport at high velocities penalizing fast forward flight regimes. Our model-based predictions suggest that long range flights require a furled tail configuration, as confirmed by field observations, and consequently need to rely on alternative mechanisms to stabilize the flight.

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Empirical Estimates of Body Drag of Large Waterfowl and Raptors

Cited by 86 publications

References 6 publications

Optimization of avian perching manoeuvres

Optimization of avian perching manoeuvres

Thermal effects of plumage coloration

On the role of tail in stability and energetic cost of bird flapping flight

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