Bird Exam 2: Flight

birds that can hover

• american kestrel

  • flapping

• red tailed hawk

  • understanding of aerodynamics

  • kiting 

backwards flying bird

hummingbirds

soaring bird

vultures

skeleton

• uniquely structured for flight

  • fusions and reinforcements

    • powerful and delicate

bone cross section

• light, air filled

• wing bones are strong

  • struts

bill

• light weight

• toothless

keel

• large chest bone

  • sternum

  • anchors flight muscles

  • size is indicative of flight abilities

wing

• modified forelimb

• fused hand and finger bones

  • strength and rigidity

two great flight muscles

• pecoralis

  • 15% of birds mass

    • chicken brest 

  • pulls wings down

    • contraction

  • power stroke

• supercoracoideus 

  • pulls wing up

  • recovery stroke

  • smaller

muscle fibers

• red

  • sustained contraction power

  • hummingbird major flight muscles are both red

• white

  • rapid, powerful contractions

  • fatigue fast due to arctic acid buildup

  • fast turns

  • evasive actions

to stay aloft

• must overcome gravity with a force that is equal and opposite 

• four forces

  • weight

    • countered by lift

  • lift

  • drag

  • thrust

    • countered by drag

  • must be in balance to maintain level flight

the airfoil

• asymmetric structure that tapers posteriorly

  • same as bird wings!

correct orientation of the wing produces a new upward force

• lift

  • based on the different speeds of air flowing over and under the wing

    • faster airspeed on upper surface = low pressure

      • less molecules

    • slower speed on lower = high pressure

      • more air molecules

  • pushes the bird upwards

angle of attack

• influences amount of lift generated

  • increase drag if you increase angle

• as rear edge of wing tilts downward increase lift is produced

slots between feathers

• allow for fine control of air movement

• vultures

  • 40% of wing surface if slots

• helps to prevent stalling

• make the primaries act as their own airfoils

drag

• any turbulence reduces lift

  • smooth overlapping feathers are very important

• drag

  • any negative fire that opposes a birds movement through the air

  • any turbulence that reduces lift

drag types

• induced

  • turbulence about the airfoil

  • decreases with increased speed

• profile

  • friction between the air and a bird's body

  • minimized by thin leading edges of wings

forward thrust

• overcomes slowing effects of drag on airspeed

• downbeat of a wing

  • powerstroke

linked to wing shape

• speed

• agility

• energy consumption

lift and drag

• vary with wing dimensions

• open country birds

  • long pointed wings

  • swallows

  • kestrels

  • shorebirds

• woodland birds

  • short rounded wings

  • goshawks

  • coopers hawk

wing loading

• relationship wing area and body mass

  • grams per cm^2

• songbirds

  • .1-.2

• albatrosses

  • 1.7

gliding flight

• wing shape influences soaring ability

• soaring flight

  • vultures

    • how forces of weight, tilt, drag work 

    • rely on wing lift to balance gravity 

    • thermals and slope soaring

• thermals

  • rising columns of warm air

  • natural force that provides lift

• slope soaring

  • air that is deflected upward when it hits terrestrial ridges or ocean waves

flapping flight

• adds thirst to the balance of controlling forces

• hummingbirds

flightless birds

• predator free islands

• maintenance and development is costly, unnecessary 

  • get to put energy in other places

  • reduced flight muscles, smaller keel bone