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Flight and other locomotion in birds

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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.

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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 3rd Law – for every action there is an equal and opposite reaction.
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

Open-billed Stork

A

1°s

Low Speed (take-off and landing)

High Angle of Attack

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

Florescent induced photo

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

Di - drag

Ve - Airspeed

Induced Drag
• Di - induced drag
• A - aspect ratio
• k - constant
• L - lift
• S - wing area
• Ve - airspeed
• ρ - air density

High speed

Low speed

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

D

Airspeed

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
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

Videler et al. (2004)

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)

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-tunnel
• 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-glide

Flap-bound

Budgerigars in wind-tunnel (Tobalske and Dial 1994)

4. Hovering
• Flapping while maintaining horizontal position
• Examples:
5? Formation Flying
• Saves energy (11-14%)
• Coupled with full belly – even more (Kvist et al. 2001)

low

high

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