Ornithology Unit 3 Flight. Flight Variations Some birds can hover Some birds can dive.
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Transcript of Ornithology Unit 3 Flight. Flight Variations Some birds can hover Some birds can dive.
Ornithology Unit 3
Flight
Flight Variations
• Some birds can hover
• Some birds can dive
More Flight Variations
• Some fly in heavy brush
• Some soar for days on end
Avian Skeleton
• The avian skeleton is strong and delicate, a combination that allows them to fly
Skeletal Adaptations for Flight
1. Hollow bones – make them lighter
2. Bones are fused together and reinforced – makes them stronger
3. Have unusual joints – make flight motions possible and brace against stress
More Skeletal Adaptations
4. Instead of a heavy jaw and teeth, they have a toothless bill - makes them lighter
More Skeletal Adaptations
5. The sternum (breastbone) has a special structure called a keel – major flight muscles are anchored here
- Flight ability is directly related to keel size
More Skeletal Adaptations
6. The skeleton must be able to withstand the stress of flight.
- They have a lot of reinforcing in the thoracic area
- Have partially fused vertebrae
Furcula
• AKA, the wishbone• Made of fused collar
bones• Works like a spring &
helps bring the wings back up after the downstroke
The Wing
• A modified forelimb for flight
• Humerus, radius and ulna are similar to ours
• Fused hand, finger and wrist bones provide strength and rigidity to the outer wing
Flight Muscles
• Pectoral – power for down-stroke
• Supracoracoideus – brings wings back up
Flight Forces
• Negative Forces
1. Gravity
2. Drag
• Positive Forces
1. Lift
2. Thrust
Aerodynamics
• A bird’s wing is shaped like an airfoil
• Airfoil – an asymmetrically curved structure that tapers at the end
• Airfoils change the speed air flows over the surfaces and creates lift (or drag)
Generating Lift
• The amount of lift generated depends on surface area of wings and air speed
• It also depends upon the “angle of attack”
• More lift is generated as the back of the wing is tilted downward
Slots Between Flight Feathers
• Aid in fine control of air movements
1. Some help to maintain lift at slow speeds
2. Air forced through from the underside, expands as it hits the top of the wing, reduces pressure and increases lift
Wing Shape
• This effects the type of flying that can be done
• Pointed wings generate less lift, produce less drag (speed)
• Rounded wings produce more lift and drag (less speed)
More on Wing Shape
• Aerial and open country birds like shorebirds, swallows and terns have long pointed wings
• Birds living in thick vegetation usually have short rounded wings
Energy Costs
• Flight costs quite a lot of energy
• It can be defined by the relationship between the total wing area and total body mass
• This relationship is called wing loading and is given in grams per square centimeter of wing surface area (g/cm2)
Calculating Wing Loading
Sample Problem: The Osprey
Information: weight = 1500g
wingspan = 165 cm
body length = 56 cm
Step 1 Calculate the Wing Width
Surface Area = Length of Wing x Width
- We don’t know the width, so we’ll need to calculate it. Cornell Lab of Ornithology says a reasonable estimate can be calculated by multiplying the body length by 1/3 (0.33). So…
- Wing width (w)=body length (b) x 0.33 or
- w=b x 0.33 so w=56cm x 0.33=18.48cm
Step 2 – Calculate the Surface Area of the Wing
Surface area = wingspan(s) x wing width(w)
so…
SA = S x W or
SA = 165cm x 18.48cm
SA = 3049.2cm2
Step 3 – Calculate the Wing Loading Ratio
Wing Loading(WL) = Mass (m) / SA
WL = m / SA so for the osprey…
WL = 1500g / 3049.2cm2
WL = 0.49g/cm2
Gliding Flight
• Flight that takes place without flapping
• Without flapping, no forward thrust is applied, so they sink because of drag
Thermal Soaring
• Uses columns of warm air rising from the ground from the sun heating the earth
• Circle in one “thermal” and rise, then glide to the base of another
Slope Soaring
• Using rising air deflected off of a ridge or ocean wave
• Migrating hawks soar along ridges and gulls are able to hang in the air behind a boat
Flapping Flight
• Flapping adds thrust
• Wings push air down and back
• Some flap constantly, others have an undulating flight pattern
• Independent control of each wing helps with steering
• The tail is also used to generate some lift and also for steering
Flightless Birds
Q: Why are some birds flightless?
A: They avoid the cost of developing and maintaining complex structures used for flight
- Flightless birds typically fill other niches (environmental roles) than flying birds
- Develop special adaptations for their niche