Lecture 8 Flashcards
1
Q
Evolution of modern, powered flight was dependent on the development of what?
Why were these adaptions so important?
A
- aerodynamic shape and structure of the body
- physiology to provide energy
These adaptions (accumulated small changes over millennia) opened up a new niche and enabled tremendous diversification of birds
2
Q
Give evidence for the reason it is believed that ability to fly (what defines modern birds) evolved for a different reason
A
A lot of the skeletal and physical adaptions that birds have were present in non-avian theropods in animals that hadn’t evolved the ability to fly so the adaptions (such as hollow bones which were still present in non-avian dinosaurs) had evolved for different reasons
3
Q
What are the two theories for how flight was evolved?
A
. Arboreal theory
. Cursorial theory
4
Q
Explain the arboreal theory of how flight evolved
A
Perhaps flight developed from parachuting and gliding from high perches (e.g. a tree-loving Theropod)
5
Q
Explain the cursorial theory as to how flight evolved
A
Perhaps elongate forelimbs (which we know were present in some theropods) gave better leaping ability and control to a small Theropod dinosaur that ran and jumped to catch insects.
6
Q
Explain how a proto-wing could help in the evolution of flight
A
A proto-wing, increased arboreal habits and gliding would be the next step
7
Q
A four-winged gliding dromaeosaur is a what?
A
A Theropod
8
Q
Describe Microraptor gui and it’s connection to the evolution of flight (give the features, age)
A
. 130M- years old
. Forelimbs resemble the wings of modern birds
. Feathers were asymmetrical:the vane on one side of the feather spine was wider than the one on the other (indication adaption to flight)
. Had feathers attached to the fore and back limbs
9
Q
Describe Pedopenna (a Theropod that had feathered legs) and it’s connection to the evolution of flight
A
A small, feathered, maniraptoran dinosaur (Aviales) from China; probably older than Archaeopteryx
. Had feathers on the hind wings
. Short fore limbs
. Animal was too heavy to fly and the wings weren’t big enough
10
Q
What is Paraves?
A
A subgroup of the Theropod dinosaurs
11
Q
What did Anchiornis predate
A
Archaeopteryx
12
Q
By 5-10 million years basal member of all three Paraves groups (Anchiornis, Microraptoe and Pedopenna) all had what?
A
Long pennaceous feathers on lower legs and feet, as well as on their hands and tail. Has feathered wings and hind limbs
13
Q
What are the names of the 3 Paraves groups?
A
. Anchiornis
. Microraptor
. Pedopenna
14
Q
By 5-10 million years basal members of all there Paraves groups had long pennaceous feathers on lower legs and feet, as well on their hands and tail. (Has feathered wings and hind limbs.) what is an implication of this?
A
That perhaps avian evolution went through a ‘four-wing’ stage
15
Q
A model that compared a Microraptor with its legs sprawled and with its legs down showed way? What does this suggest about the evolution of flight?
A
Showed better simulation if you have feather on the hind limbs to hold them down. So feathered legs can help gliding.
Perhaps when flapping was used to power flight it may have lessened the new for feathers on the hind limbs completely so it could be a secondary loss
16
Q
Whu is there a debate that the Arboreal theory of the evolution of flight is a false dichotomy?
A
Assumes flight developed by gliding, but this is a derived character absent in basal avian groups
17
Q
Why is there a debate that the Cursorial theory of the evolution of flight is a false dichotomy?
A
No extant species uses wings to run faster, secure prey or run-glue (don’t use their wings to capture prey)
18
Q
It was proposed that ontological development recapitulates evolutionary development, explain what this is
A
The development of the animal in the womb reconfigures the evolutionary stages that, that species has gone through to develop into what it currently is. So, by looking at embryonic development you can work out the stages of evolution it went through
19
Q
What is the transition of proto-wing to powered flapping flight limited by?
A
Relative size of wings and muscle power need the right muscles to give the animal power to move
20
Q
What does WAC stand for?
A
Wing-assisted climbing
21
Q
Give examples of some modern species of birds that have lost the ability to fly
A
. Ostridge’s
. Penguins
22
Q
What are the elements of flight (needed to be able to fly)?
A
. Aerodynamics (body shape)
. Feathers (act as a flight surface)
. Mechanics (to get airborne and stay airborne)
. Respiration
23
Q
Wings need to provide lift but also to minimise the energetic cost of flight. How is this done?
A
. Streamlining . Boundary layers . Turbulence . Pressure drag . Maintaining laminar flow
24
Q
What is laminar flow?
A
Flow of air over the flight surface and over the body of the bird
25
What is turbulence?
Air breaking up around the flight surface (need to miniseries drag)
26
What are the four basic forces acting on a flying object?
. Lift (to stay in the air)
. Thrust (so it can move forwards)
. Drag (the force holding back the animal)
. Gravity (pulling it down)
27
High lift in flight is produced by what?
. High air flow
. Increased effective curvature of the wing (air has for further to go to get from front to back when it goes over the top)
28
What is stalling?
When the air flow breaks up and is no longer laminar
29
What happens as the angle of attack increases?
Laminar flow tends to break up towards the back of the wing , leading to stalling and reduced lift
30
What is Bernoulli’s law?
For a moving fluid (or gas), pressure is inversely related to velocity of flow
31
What does slower moving air on the underside of the wing exert?
More pressure than faster flowing air moving over the top= lift
32
If the bird wants to fly at a lower speed what does it do?
It can increase the angle of attack, lift and drag will increase, due to the fact that you have increased lift the bird can stay in the air
33
When the angle of attack increases over 15% what happens?
The air flow at the top begin to break away from the airflow and leaves turbulence behind and when that forms the wing stalls and when that happens the pressure difference goes away and the bird falls out of the sky
34
The stalling angle can be increased by a small pet of the wing called the what?
Alula (adds a little bit of additional airfoil)
35
What is the alula?
A small group of feathers on the first digit of a forelimb
36
What is critical to maintenance of lift?
. Smooth flow of air over wing surfaces
| . Laminar flow (as opposed to turbulent flow)
37
What happens when the angle of attack is increased?
Greater lift and drag, speed slows own, but increased lift keeps bird aloft
38
What is the stalling angle? What part of the bird serves this function?
The angle of attack can be increased by slot that forces air to conform to surface of wing
The alula or bastard wing of many birds serves this function
39
What happens when the angle of attack increases above 15%?
. Laminar to turbulent flow
. Lift is lost
(. Stalling angle)
40
What are the 2 main sources of drag on a flying bird? Explain them (when they increase and decrease and what it is caused by)
. Profile drag ( the shape)- sir dragged along by moving body- increased with speed
. Induced drag- resistance to laminar flow around wing- decreases with increased speed
41
Give the flight adaptions
. Hollow bones
. Strutted bones
. Lightweight toothless bulls
. Flight surfaces
42
Explain how the adaption of hollow bones helps flight
. Light per unit mass
. Adaption to reduce weight
(But they were present in non-avian theropods they must have evolved for some other purpose)
43
Explain how the flight adaption of strutted bones helps flight
High strength in relation to mass
44
Explain how the flight adaptions of lightweight toothless bills assists flight
The centre of gravity is moved to the middle of the bird. Grinding apparatus is in the gizzard: a muscular stomach. By moving the grinding function of the head from the centre of the body to the stomach it makes the animal better balance for flight
45
What is relevant to consider about feathers with avian animals? (Talk symmetry, flight surfaces)
. Edge on to the low of air, symmetrical feathers are unstable
. But overlapping layers of symmetrical feathers form a flight surface
. edge-on to air flow, an asymmetrical feather is stable and can function as an independent aerodynamic unit
. Consider WAIR- don’t new goo aerodynamic feathers to achieve this
. Increasing flight surface by outstretching forewings- aerodynamics and feathers stability at leading edge become important
46
Discuss the tail as a flight surface (feather asymmetry)
The outer-most tail feathers are asymmetrical-so the central shaft is near the leading edge of the feather- has a short outer web and a wide inner web. The middle feathers are much more symmetrical because they are very rarely end on to the flow of air, so they don’t need to be asymmetrical. The outer feathers are also very long and thin because they are adapted to aerodynamic functions
47
How do we know that a lot of ‘flight adaptions’ didn’t evolve for flight?
Because they are present in non-avian theropods
48
Give the adaptions of bones and joints of pectoral girdle for flapping flight (and associated musculature) (a lot o these adaptions are present in non-avian theropods and therefore they must have evolved for something other than flight)
. Large sternum or keel (carina)
. Rigid thorax
. Pectoral girdle
49
How does the flight adaption of a large sternum or keel (carina) benefit avian birds?
Large sternum or keel to anchor pectoral muscle, giving a long pull and high mechanical advantage. Flying ability tends to correlate with relative size of keel. Birds that are very strong flyers have a very deep keel (a long or a very deep keel allows the muscle to have a good pull and a high mechanical advantage)
50
How does the flight adaption of a rigid thorax benefit avian birds?
Fully ossified dorsal and central ribs (because there is no cartilage), strong connections between backbone and breastbone, uncinate processes (boning processes) reinforcing the ribcahe
51
How does the flight pectoral girdle have benefit avian birds?
pectoral girdle: Scapula, coracoid and furcula (clavicle) forming a triangular system of strutted that resist the crest-crushing pressures created by the wings (wing muscles) during flight
52
What is the humerus?
The first part of the forelimb
53
What is the furcula?
Attached to the front* part of the keel or sternum
54
What is the coracoid?
Connects the sternum to the humerus and the furcula
55
How does the radius help the bird?
Large joint surfaces allow folding neatly against the bird
56
What does the forelimb consist of?
The ulna and radius
57
What does the carpometacarpus?
The carpals and the metacarpals fused together form from carpometacarpus
58
What are the flight feathers inserted over?
The hand (primaries) and radius/ ulna/ humerus (secondaries, tertials*)
59
Embryonically what are the digits in the outerwing skeleton or bird equivalent to in mammals?
2, 3 and 4
60
What is the reason that the first digit is flexible?
So that it can provide extra skid aerofoil o the wind to maintain kamikaze flow
61
The ulna and radius have large joint surfaces and those joint surfaces allow what?
Allow the high degree of movement that the forelimb requires to be folded over the back when not in use and a high degree of rotational flexibility to facilitate different type of flight
62
Relative length of wing bones depends on species and function. Give 2 contrasting examples
Albatross- a specialised dynamic glider, uses its wings to provide lift, lift from secondaries is important hence long radius/ ulna and lots of secondaries
Hummingbirds- long hands to generate thrust is important, hence the radius/ulna is relatively short and the primaries play an important role in their generation
63
What are the main thrust generators of the avian wing?
The primary feathers and the carpometacarpus
64
How many primary feathers are there over he hand of a bird?
10
65
Where are the secondary feathers and what are they important in?
They are over the ulna, radius and humerus and are important for generating lift
66
What are the names of the 2 main flight muscles?
. Pectoralis (Major)
| . Supracoracoideus
67
In many species the pectoralis muscle represents about what percentage of the total mass of the flying bird?
15%
68
What does contraction of the pectoralis do? What does it represent?
Pulls the wing down (the main work cycle) and generates thrust.
Powers the downstroke and represents the highest proportion of the mass of the bird than any other muscle (main power generating of the wing beat)
69
Why is the Supracoracoideus muscle important?
It is important for the recovery stroke, especially during take-off- needs to bring the wings up quickly and as high as possible to allow the next power downstroke (pulls wins up)
70
What happens if you cut the supracoracoideus? Explain
If you cut this tendon then the bird cannot take off but an fly because some of the dorsal elevator muscles can do some of the work
71
What is the upstroke aided by?
Small dorsal elevator muscles (if you cut the supracoracoideus tendon the bird can’t take off but can fly in level flight perfectly well)
72
Where is the supracoracoideus oriented? What does it attach to and why?
Along the base of the keel (or sternum) and goes up a canal between the humerus and the furcula to attack to the humerus so it can pull the wing back up again (is a more compact comical muscle along the base of the keel)
73
What is the key difference between the pectoralis and supracoracoideus muscles?
The orientation of he muscle fibres
74
What is the pectoralis he main part of? How are the muscle fibres oriented?
The main part of the breast muscle of the bird
| Oriented backwards
75
What are he 4 general wing shapes?
. Elliptical wings
. High speed wings
. High aspect ratio wings
. Slotted high-loft wing
76
Describe elliptical wings
. Short (low aspect ratio)
. Often highly slotted to allow separation of primaries
. Increase lift, especially at slow speeds
. Short wing length higher wing beat frequency, rapid takeoffs, quick acceleration, rapid turning
77
What habitat do birds with elliptical wings usually live? Give examples of some species that shave this type of wing
Birds of shrubby habitats or forest habitats
| Galloform birds, some doves, woodpeckers and many passerines
78
What is meant by aspect ratio?
Ratio of length to width of wing
79
What does the spreading of wings provide?
Additional slots to maintain laminar flow of the wing surface
80
Describe high speed type of wings and give examples of birds with the type of wing
. Birds that feed in flight and/ or long-distance migrants (tend to have wings which are longer)
. Low camber (flat profile)
. High aspect ratio (long and slender)
. Taper to slender tips, no slots
. Pointed tips minimise induced drag
. Long wing separates vortices (shredding from the if top and keep those away from the lift generating surfaces of the secondary feathers)
. Greater proportion of wing effective for generating lift
. Shore birds (predator escape and long-distance migration), swifts, hummingbirds, falcons, swallows (very good predator avoidance strategy having that as a flight wing shape). An extreme example is an artic turn, swifts, Falcon, all fast flyers
81
Describe the high aspect type of wings with examples
. Soaring sea birds- albatrosses (extreme), frigate birds, kittiwake* (not as extreme)
. Extremely long, narrow, no slotting (sometimes bent carpal joint, sometimes not)
. High speed flight
. Dynamic soaring
82
Describe slotted high-lift type of wings, give examples, habitat, adaptations
. Moderate aspect ratio (fairly long but. It as long in width in relation to an albatross)
. Deep chamber (wing shape has a high curvature- good airfoil shape), high slotting
. High lift at slower speeds(which is why they are quite broad), narrower turning radius
. Mostly terrestrial birds that soar a lot
. Hawks, owls, buzzers, eagles, predators carrying heavy loads (back to the nest)
. The end of the wing/ fingers are formed by adaptions to the shape of the feathers- narrowing of the feather towards the tip gives rise to this slotting- so when the wing is fully extended these slots become apart and that is an adaption to get higher lift at low speed and that slotting maintains laminal flow over the wing
83
What is meant by gliding and soaring?
Flight without flapping
84
Describe gliding
. Evolved in several other vertebrates
. Delay rate of descent by maintaining forward movement
. May alternate gliding with soaring (or periods of flapping) to gain altitude
85
Describe soaring. Give the two types and example them
. Maintain or increase altitude without flapping
. Two methods:
- static soaring- using currents of rising air
- dynamic soaring- using horizontal layering of air currents differing in velocity (bay in air currents)
86
What are the requirements of gliding and soaring?
. Large size (minimise disruptive effects of turbulence)
. Low wing-loading (large wings in relation to their body mass), high manoeuvrability
. Good turning ability
. Soaring birds may have relatively small breast muscles and relatively shallow levels because they don’t need to put as much energy/ power into moving the wings to envelop thrust (low-for flight)
87
What are the names of the two types of static soaring?
. Thermals
| . Obstruction currents
88
Explain the type of static soaring, thermals (how it works, what it is associated with and give an example)
. Convection currents due to unequal heating of ground
. Associated with cumulus cloud formation
E.g. on a relatively hot day you can see buzzers and gulls flying around in circles with their wings outstretched and they are using the rising currents of air to maintain height- uses very little air
89
Explain the type of static soaring, obstruction currents (how it works, give examples)
. Wind hits land obstruction and is deflected upwards- e.g. when the wind hits a cliff it moves upwards and birds can use that air to dry aloft
. Wind hits boat on water surface e.g. gulls following behind boats that are using the air rising over the boat to stay in the air without using much energy
90
Static soaring requires high manoeuvrability (because birds have to try and stay within the rising current of air.) What features do the birds have for this?
. Longer tail and relatively short (in relation to their width because they need to turn in spirals to stay in the rising currents) broad wings (for good manoeuvrability)
. Turn in right spirals to stay in rising currents
. Slow speed needed to stay in thermal
. High-camber, high slotting- increase lift at low speeds
91
Explain dynamic soaring with an example
Natural velocity gradients in air speed e.g. wind at wave/ water surface- because air will be slowed down y pressure of the surface and as you move up the wing speeds will pick up so birds can use those speed differentials to maintain speed
92
With flapping flight why is there variability throughout wing stroke cycle?
. Angle of attack
. Orientation of wing relative to body
. Extensive rotation and bending at the shoulder, elbow and wrist
93
In flapping flight the secondaries stay relatively stationary in sustained flight. Why is this?
Provides most of lift level forward flight
94
What do birds when they are taking off? How is this different to normal flight?
. Wing beats deeper, faster
. More rotation at wing joints
. Little forward speed because no lift from air flow over wing- has to put a lot of energy into getting off the ground and moving forward over the air to generate enough air over the wing to give it lift
. Wing moves downward and forward to generate air flow over surface
. Low speed: critical to generate lift without stalling
. High angle of attack, slotting of primaries
. Use of alula: some birds cannot take off if alula are removed (alula and the slotting of primaries is very important in take-off to maintain laminal flow over the wings)
95
What are the additional methods used to generate forward speed for take-off?
. Diving off perches, cliffs
. Paddling, running across surface e.g. grebes, ducks- to build up speed in order to take off
. Jump upwards with thrust from legs- heron,egrets in order to gain height so that they can move through the air faster
96
Explain hovering flight of hummingbirds (energetically expensive)
. Highly adapted wing structure (produce lift throughout the air stroke cycle- move their wing through a figure of 8 through each wing stroke): most of wing is hand
. Upper arm and forearm reduced- elbow and wrist rigid
. Most rotation at shoulder (almost 180 degrees): high degree of rotation
. Wing moves backward and foreword in shallow figure 8
. Dorsal surface faces down on backstroke, central surface faces down on forestroke: lift generated in all phases
. Stream of air directed down in hovering bird, forwards or backwards in moving bird
. Backwards flight possible
. They feed on things such as nectar that is high in energy so that they can sustain this high energy flight mechanism because it is very energetically expensive
97
Describe hovering: how birds do it/ why they are able to, how is it carried out
. No kinetic energy to provide air movement over wing
. All lift generated by wing movement
. High energy requirement
. Wing elevator muscle is half size (the supracoracoideus large relative to the pectora muscle) is quite of pectoralis (1/9 in typically bird)
. Breast muscles 30% of birds weight (a much higher proportion of the body weight compared to any none hovering bird)
. More efficient than expected because wingbeqt (wing cycle) creates trailing current (air current), generating unexpected increases in lift) next strike moves through in current in opposite direction
98
Why is formation flying advantageous? How does it work?
. Advantageous, especially to larger birds. It is advantageous because birds behind the leader can gain energetic advantages- reduces energy costs because they are using the air currents that are set up by the leading bird. The bird at the front is doing the most work. Don’t want to be the leader for very long so the leader is changing all time- very dynamic
. V formation birds behind the leader are regularly spaced: end of time is in wing top vortex of bird ahead upward movement of air gives extra lift
99
How do Pelicans use formation flying?
Energy saving formation- pelicans flying in a ‘V’ can glide for extended periods using the other birds air streams
100
Give examples of birds that use formation flying
Swans, geese, gulls
101
A bird flying in upwash regions gains free lift- what does this mean for the bird?
```
. Can fly at a lower angle of attack
. Lower induced drag
. Lower work rate
. Heart rate drops
. Bird can fly further
```
102
What can proper spacing do in formation flying?
Drag of every bird can be reduced
103
In formation flying do all the birds benefit equally? How can this be helped- explain?
Not all benefit equally: lead has to work the hardest but gain some reduction in drag: two birds flanking help to dissipate the downwash off the lead birds wingtips and reduced the induced drag.
Flanking birds also benefit from a similar reduction in drag of outboard birds flank them as well
104
In formation flying which birds are in the best position? Why is this the best position?
The birds in the middle of each of the lines are in the best position: benefit from upwash off lead birds and trailing birds
105
In the early 1900’s how many species of bird was there thought to do? How many do the think now?
19,000 species
| 8,600 approx
106
Why has the estimated number of bird species changes between 1900’s and now?
. Races not now differentiated as species
. Age/sex categories described as species now in their proper place- we didn’t know enough about plumage patterns in different types of birds
. Species count changes as new taxonomic methods e.g. DNA analysis are used
107
What did early attempts at classification of birds use?
Superficial similarities to group birds e.g. land birds/ water birds
108
What characteristics were used to classify birds in the early attempts at classification?
. Palatal structure
. Nostril form on top of the bill
. Leg muscles, foot and tendon arrangement
. Arrangement of toes
. Scales on tarsus
. Behaviour, call, plumage patterns, plumage patterns on downy young
. Biochemical features (now a days DNA has taken over)
109
Birds in general comprise two broad groups. What are these?
. Ratites
| . Carinates
110
Describe the bird (broad) group ratites (examples, what they are characterised by etc.)
. Flightless birds such as Ostriches, Emu etc.
. Characterised by a raft-like sternum
. A palaeognathous palate structure
111
Describe the (broad) group of birds Carinates
. Flying birds
. Keeled sternum in which powerful flight muscles insert
. Neognathous palate (small vomers, large palatines, pterygoid not reaching vomer articulation)
112
To see the difference between the two different types of palates is quite a fine detailing. How is it done?
You have to look underneath the skull to see how the bones articulate
113
The avian skull essentially consists of 4 bony units. What are these?
. An upper jaw/ braincase complex
. Pair of pterygoid bones
. Pair of quadrate bones
. Mandible
114
How many orders are in carinates? Give 4 examples
```
About 22
. Podicipediformes
. Anseriformes
. Pelicaniformes
. Cicoiiformes
```
115
What order are grebes in?
Podicipediformes
116
What order are water fowl (ducks, geese and swans) in?
Anseriformes
117
What order are marine birds (pelicans, cormorants, anhingas)
Pelicaniformes
118
What order are wading birds (egrets, herons, ibises, spoon bills and storks) in?
Ciconiiformes
119
Unique features may define related groups of species. Give an example
Song birds (Passeriformes) have several unique features:
. Peen gland with a unique nipple structure
. Unique sperm morphology
. Specialised preaching foot with a rear-directed toe (Hallux)
120
What is a rear-directed toe called?
Hallux
121
Why do a lot of unique features arise in the group Passeriformes?
Because it is monophyletic- has a common ancestor
