# Flight and other locomotion in birds. Lift of a wing Bernoulli effect – pressure is inversely related to number of particles moving in a single direction.

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Flight and other locomotion in birds

Lift of a wing Bernoulli effect – pressure is inversely related to number of particles moving in a single direction (fluids). Newton’s 3 rd Law – for every action there is an equal and opposite reaction.

Static airfoil (wing)

Angle of Attack Vacuum If angle of attack > ~5°, wing starts to produce vorticies. These can lead to “stall”

Solution = alula (bastard wing) Particularly important at low speeds and high angles of attack

A 1°s Open-billed Stork Low Speed (take-off and landing) High Angle of Attack

Landing

Sanz et al. 1996 Nature Eoalulavis hoyasi Los Hoyas, Spain Goldfinch sized bird 115mya 30my after Archaeopteryx = low speeds = high maneuverability Florescent induced photo Eoaluavis

Drag Resistance caused by friction of air moving over the surface of the wing Induced drag occurs when the air flow separates from the surface of a wing –Air moves from high to low pressures –“fills” vacuums created by wing Profile drag is due to the friction between the air and bird moving through the air –Minimized by “low profile” (aerodynamic anatomy) –i.e. thin leading edge of wing

Induced Drag D i - induced drag A - aspect ratio k - constant L - lift S - wing area V e - airspeed ρ - air density V e - Airspeed D i - drag High speed Low speed

D is the force of drag,force ρ is the density of the fluid*,density v is the velocity of the object relative to the fluid,velocity A is the reference area, andarea Cd is the drag coefficientdrag coefficient Profile Drag Airspeed D

Drag Curve aka Profile drag

2 gaits of a bird –Vortex-ring gait Low speeds –Continuous-vortex gait High speeds

Flight Recap Amount of drag is affected by: –Body size –Speed –Wing’s surface area and shape –Environmental factors Viscosity etc.

Wing shape Aspect Ratio – Length / width –Range = 1.5-18.0

Gliding Wing Laysan Albatross

High Speed Wing

Explosive, Maneuverable Wing Grouse Wing

Contribution of the hindlimbs Varies over species –May be very important (Starlings 80-90% of take-off velocity due to hindlimb contribution) Earls 2000

Hummingbirds –46-59% –Variability depends upon motivation Autonomous – 59% Escape – 47% Aggressive (chasing conspecific male) – 46% Tobalske et al. 2004

The leading edge Vortex The “LEV” of a swift Low pressure zone On top of wing Wing wants to “fill” the low pressure zone thereby creating lift Can be used for maneuverability (each wing independent) Videler et al. (2004)

Wing slotting

Different Modes of Flight 1. Gliding – Vs/V (sinking speed – horizontal speed) –Glide ratio of 20 2. Soaring – maintain altitude w/o flapping. –Thermals (see drawing) and updrafts (“slope soaring”) –Dynamic soaring “Obstruction lift” Or “slope soaring”

Hawk mountain east Kettle valley

Dynamic Soaring 1 - climb (windward flight); 2 - upper curve (change of flight direction to leeward); 3 - descent (leeward flight); & 4 - lower curve (change of flight direction to windward) (Sachs 2005). video

3. Flapping flight Video of a starling in a wind-tunnelVideo Downstroke (“power stroke”) – flex wing depressors - lift. Upstroke (“recovery stroke”) – flex wing elevators - minimize drag. –Slotting Cockatiel flying at 1m/sec

Flapping (cont) Flapping is usually intermittent in small species And varies w/ speed Flap-glideFlap-bound Budgerigars in wind-tunnel (Tobalske and Dial 1994)

4. Hovering Flapping while maintaining horizontal position Examples:

5? Formation Flying high low Saves energy (11-14%) Coupled with full belly – even more (Kvist et al. 2001)

Note on metabolism and flight Predicted Observed

Other forms of locomotion in birds Running, walking, hopping, waddling –Head bobbing –Ostriches Climbing –Nuthatches, woodpeckers Swimming –Ducks Diving –Penguins, Auks

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