Lab 6 Flashcards
Bird flight adaptations
Digits greatly reduced/lost
Feathers
Pygostyle
Flight is powered mainly by breast muscles
Keeled sternum
Pneumatized bones
Digits greatly reduced/lost
Only digits 1 through 3 contribute to wing skeleton
Feathers
Make up bulk of wing and tail
Pygostyle
Bones of tail reduced and modified
Keeled sternum
Concentration of muscle placed on keeled sternum keeps center of gravity low and aligned with wings
Pneumatized bones
The hollow structure of bird’s bones help to lighten the skeleton
Wing basic structures
Alula
Primary wing slotting
Alula
The first digits of a bird’s wing bears the alula
When spread away from the rest of the wing and angled the alula created a wing slot that redirect air over the upper surface of the wing
This prevents stalling when the main airfoil of the wing is pointing upward
Primary wing slotting
The primary feathers of some birds have a distinct constriction near the tips
When spread out, they create wing slots which reduce drag created by vortices at the wing tips
Aspect ratio
Simply the ratio between the length and width of the wing
A long narrow wing will have a high aspect ratio
Camber
The ventral concavity of the wings surface
Wing types
Elliptical
High speed
High aspect ratio
High lift
Elliptical wings
Wings with a low aspect ratio
Typical of birds that inhabit dense environments such as forests
Elliptical wings maximize surface area and lift
Enables a high degree of maneuverability in a compact form
High speed wings
Wings with a medium/high aspect ratio and very low camber
Maximize thrust and have a reduced surface area and camber making it easier to rapidly beat the wing
High aspect ratio wings
Excellent air foils (like plane wings) but stay at low speeds
Long distance birds
Rely on consistent strong winds to increase the air speed moving over the wing enabling the bird to stay aloft by angling the wing upward
High lift wings
Wings with a medium aspect ratio, high camber and obvious primary wing slotting
Maximize lift generated with each wing beat or from upward moving air currents
Soaring types
Static soaring
Dynamic soaring
Static soaring
static soarers keep aloft by seeking out air currents that rise vertically as a result of hot air rising or of deflection off a large obstruction
Fly in a circle above the rising current
Will glide between pillars of rising air to glide
Dynamic soaring
Angle their wings upward in opposition to horizontally directed wind currents to quickly gain altitude
Once high enough, the bird will glide downward in the direction of their choosing
When altitude becomes low, the bird will again direct itself into the wind, repeating the cycle as before
Have high aspect ratio wings
Bird skull features
Modified diapsid
Cranial kinesis
Loss of teeth
Keratinized beak
Modified diapside
Reduction and loss of temporal bars associated with reduced bite-force and increased flexibility compared to other archosaurs
Cranial kinesis
The skulls of most birds are highly kinetic
Loss of teeth
Often cited as a weight reducing adaptation
Keratinized beak
Much lighter than teeth
Food acquisition and processing
Carnivorous bird bills
Relatively short, strong and hooked at the tip
Carrion feeders bills
Very similar to carnivorous but still slightly longer for more efficient removal of flesh from a carcass
Fish eater beaks
Serrated
Narrow bill with serrations for shearing flesh and a hooked tip to help grip struggling fish
Fish eater beaks
Dagger shaped
Long, strong, pointed bill used for spearing and killing fish
Fish eater beaks
Pelican
Capable of capturing large prey and includes a lard throat pouch which can expand the mouth cavity to accommodate large fish
Hooked tip
Probing bills
Used to probe substrates for invertebrates
More sensitive and flexible (cranial kinesis)
Capable of opening at the tip to better manipulate or grasp food
Sieves
Some wading birds use bristle along the bill margin to filter out invertebrates from the substrate
Insect eaters bills
Small thin
Bills are for insect generalists
Thin bills are usually needle-like, for probing, or slightly hooked at the tip for catching fast moving insects
Insect eater bills
Triangular bill
Have a broad base and correspondingly large gape when fully opened
Typical of birds that catch insects in mid-air triangular bills are often accompanied by bristle-like sensory feathers surrounding the mouth
Insect eater bills
Chisel shaped
Long bills that are pointed and strong and used for boring holes into wood in search of insects
Fruit eater bills
Generally short bill with wide gape for whole berries
Seed eater bills
Typically short, strong and conical, seed eating bills vary in size according to the seeds eaten
Cross-bills
A specialized form of seed eater, crossbills spread the upper bills laterally in order to extract seeds from cones
Nectar feeding bills
Long, extremely thin bills correlate with type of flower fed upon
Grazer bills
Generalist feeding on buds, berries leaves and insects usually have chicken-like beak
Many ducks and geese graze on aquatic or terrestrial plants using lamellae to grip and cut
Carnivorous bird feet
Raptorial feet
Sharp, strong recurved claws used to immobilize, kill and transport large animals
Advantages of auditory communication
Sound passes around objects and vegetation
Can provide greater specificity and complexity than chemical communication
Can be precisely timed
Effective at night or in dark environments
Can travel over long distances
Disadvantages of auditory communication
Sound may alert predators to the location of the sender
Calls can be energetically expensive to produce
Plumage
Compliment of feathers
Types of feathers
Contour
Semiplume
Filiplume
Bristles
Down
Contour includes
Remiges (asymmetrical flight feathers of the wing)
Rectrices (symmetrical tail feathers)
Contour feathers
Contour feathers define the outer shape of the bird’s plumage
Semiplume feathers
Structurally between contour and down feathers, mostly used as insulation
Filoplume
Thin elongate feathers that have a proprioceptive (sense position of other feathers) function and may provide sensory info related to wind speed/direction
Bristles
Short hair-like structures used as tactile sensory organs
Down feathers
Short unstructured feathers positioned under contour and semiplume feathers for insulation
Scales
Epidermal scales cover the exposed legs and feet
Modified scales
Bird foot morphology is variable and tied to different forms of locomotion
Claws and talons
Homologous with the claws of other amniotes bird claws are composed of an unguis and subunguis
PIgments
Melanin (brown and blacks)
Carotenoids (bright yellows/reds)
Porphyrins (Red/brown/green)
Structural coloration
Internal structure of the feather causes certain wavelengths of light to be reflected
Most blues, greens and iridescence rely on structural coloration
