Evolution and Diversity of Birds Flashcards
What feature defines birds?
Feathers
What living tetrapod group is the closest relative to birds and what is the name of their shared common ancestor?
Crocodilia
Archaeopteryx
What is the scientific name for birds?
Aves
What were the four main features of Archaeopteryx?
Feathers
Wing claw (reptilian)
Toothed beak (reptilian)
Long tail with many vertebrae (reptilian)
Name the 5 types of feathers possessed by birds
Contour Semiplum Filoplume Bristle Down
What are the features of contour feathers?
Gives bird smooth characteristic shape Helps with streamlining of flight Flight and tail feathers are modified versions of contour feathers First level of defence Visual colouring
What are flight feathers also called?
Remiges
What are tail feathers also called?
Retrices
What two pigments are used in visual colouring of contour feathers?
Melanins (black/grey/tan)
Carotenoids (red/orange/yellow)
Which of the two pigments used in contour feathers can only be obtained from the diet of birds?
Carotenoids
What two structures use incident light to give colour to contour feathers?
Reflectance (blue/green)
Interference (iridescence)
UV reflectance also important
What is the name for a bird’s distinctive outer covering?
Plumage
What are the three parts of contour feathers holding them in place?
Rachis
Barbs
Barbules and hooks
What is the rachis?
Hollow, central shift providing backbone
What are barbs?
Extend either side of the rachis - the site of most pigments
What are barbules and hooks?
They create stiffness and flexibility and fasten feathers to one another
What are the characteristics of down feathers?
Much smaller than contour feathers
Lack barbules and hooklets
Soft and fluffy
Insulation
What are the characteristics of semiplume feathers?
Intermediate in shape
Found between contour and down feathers
Help with insulation and to keep form of contour feathers
What are the characteristics of filoplume feathers?
Hairlike - a few barbs at tip
Covered by other feathers
8-12 found around each contour feather
Pressure and vibration receptors to keep contours in correct shape and form for the environment
What are the characteristics of bristle feathers?
Stiff, a few barbs
Occur around eyes and mouth of a few bird species
May be protective / act as a filter / act as funnels for insectivores
What is crypsis?
Blending into background to avoid detection by predators or prey
Behavioural traits to match
What are the two purposes of the appearance of feathers?
Crypsis (camouflage)
Attraction - brighter males attract more mates, whilst females drab to escape predators
Why is it so important that feathers insulate birds?
Vital for endothermy - birds have body temp of around 40 degrees - higher than mammals
Fender plumage in winter
Why do birds preen?
Restores feather structure, cleans plumage of ectoparasites and dirt
Applies waterproofing oil
Allows bonding as birds prune each other
What are the 5 ways birds take care of their feathers and allow replacement of feathers?
Preening Bathing Sunning Anting Moulting
What gland in birds produces oils for waterproofing?
Uropygial gland
What is the name for when birds preen each other allowing bonding?
Allopreening
How do birds bathe and what is the issue with it?
In water or sand, but birds are vulnerable to predation afterwards as they are waterlogged so cant fly as effectively
Why do birds use sunning?
To gain vitamin D
To soften old waxes so they can be removed more easily
To make ectoparasites more active so they can be spotted more easily
What is anting and why is it done?
Birds lie on ant nest and allow ants to crawl on them
Ants produce formic acid which may benefit the birds by killing mites
Ants may remove ectoparasites
What is moulting and how often does it happen?
Replacing old feathers with new ones in orderly predictable sequence
At least once a year
Why can moulting have issues?
Takes lots of energy so not done when breeding / migrating
Besides feathers, what other features do birds possess?
Forelimbs modified as wings
Feathered tail - no bones so lighter
Toothless horny beak - teeth too heavy
Endothermy - can live in extreme environments
What 4 major groups of animals have evolved flight?
Pterosaurs
Bats
Insects
Birds
What 5 adaptations have birds got that allow them to fly?
Feathers Lightening of body Strengthening of skeletal structure Large brain and sensory organs to process sensory info Wings
What are the characteristics of feathers that help birds to fly?
Insulation Lightweight Strong Makes bird streamlined Surface is flexible
How has a bird reduced it’s weight for flight?
Lighter skeleton - reduced number of bones, bones hollow and lack marrow, skull has lost heavy jaw
Beak is toothless
Reproductive organs enlarged seasonally
Oviparous (eggs laid then incubated externally)
How is the skeletal structure strengthened?
Fusion of bones - keel and wishbone
Muscles - to power flight
What muscle powers the downward movement of wing and what percentage of a bird’s body weight is it?
Pectoralis
Up to 35% of body weight
What muscle pulls wing back up after downward movement?
Supracoracoideus
What is the keel of a bird?
A ridge along the breastbone of many birds to which the flight muscles are attached
What is the wishbone and what is it’s other name?
Furcula
A forked bone found in birds formed from the fusion of the two clavicles, which strengthens the thoracic skeleton to withstand the pressures of flight
What is the clavicle?
Collarbone
How many other wing muscles are there besides the pectoralis and supracoracoideus?
48
What is a bird’s main sense?
Sight
Why do birds have comparatively large brains and eyes?
To process large amounts of sensory information during flight
How are wings shaped - describe
AIRFOIL shape, rounded front edge and tapers down to point at rear
What are the two sets of opposing forces that bird’s must balance to fly?
Lift and weight
Thrust/propulsion and drag
What is weight and how to birds act against it?
The result of gravity - bird’s must reduce their weight as much as possible
What is lift and how does it help to overcome weight?
Generated by air flow across the two surfaces of the wing, due to airfoil shape
On the top of the wing, air has further to travel and speeds up, so air pressure is reduced and the wing is sucked upwards
On the lower side of the wing, air has less distance to travel so air pressure increases, pushing the wing upwards
What principle does the generation of lift rely on?
Bernoulli’s principle - the faster air moves, the less pressure is created
What are the two types of drag?
Friction drag
Induced drag
What is friction drag?
Consequence of air flow over body - resistance to anything passing through the air
What is induced drag?
Consequence of air foil shape and lift force - swirling vortices created at wing tips, which produces downwash
Why do birds fly in V formation?
Those in the wingtip vortices of others get an energetic benefit
How is propulsion/thrust created?
Created when wings flap, majority of this force comes from powered down stroke
What are the 3 types of flying?
Gliding
Soaring
Flapping
Hovering
What is gliding and what type of birds use it?
Weight used to overcome air resistance to forward motion
Used by heavier birds
What is soaring?
Maintaining or increasing altitude without flapping
What is slope soaring?
Using the wind deflected upwards by the side of objects such as a cliff to soar
What is dynamic soaring?
Local updrifts (caused by waves) create wind for soaring
What is thermal soaring and how do birds fly in thermals?
Uneven heating of air generates convective currents that cause air to circulate in a spiral shape
Birds in thermals fly in circles
What are the 3 types of soaring?
Thermal
Slope
Dynamic
How do birds fly by flapping and what is the result of flying this way?
Asymmetrical wing actions
Steering and turning controlled by numerous muscles
Adds thrust
What is hovering?
Maintaining a stationary position in the air
What are the two types of hovering?
Windhovering
True hovering
What is windhovering?
Flying into headwind and using thrust to fly slowly
What is true hovering?
Wing uses airfoil shape in up and down stroke
Uses a lot of energy
E.g. hummingbirds
What are the 4 wing shapes?
Elliptical
High-speed
Soaring
High-lift
What is the equation for wing loading?
Body weight / wing area
What does low wing loading mean?
Large wing area for a particular body weight - more effective flight and less energetically costly
What does high wing loading mean?
Small wing area for a particular body weight - hard to take off
E.g. swans must run along water surface
What’s the equation for aspect ratio?
(wing area)^2 / wing breadth (width)
Gives 4 types of wing
Features of elliptical wings
Low aspect ratio
Good manoeuvrability
Fast take off (important for bird’s that forage on ground)
These wings create huge amounts of drag so have slotting
What is slotting?
Gaps between feathers at back of wing to reduce drag
Examples of birds with elliptical wings
Woodpeckers
Forest raptors
Pheasants
Grouse
Features of high-speed wings
Relatively high aspect ratio Almost flat profile Great for aerial feeding These birds sleep, mate and feed whilst flying Good for long migrations
Examples of birds with high-speed wings
Swallows
Swifts
Shorebirds
Features of soaring wings
High aspect ratio
Narrow, pointed shape reduces drag
Good for sea birds in windswept environments
Examples of birds with soaring wings
Albatrosses
Kestrels
Terns
Features of high-lift wings
Moderate aspect ratio Carry heavy load and minimising energy Heavily cambered (curved airfoil wing) Terrestrial soaring species Also have wing slotting
Examples of birds with high-lift wings
Eagles
Vultures
Storks
What are the 3 behaviours flight is most important for?
Feeding
Courtship
Migration
What is an example of flight being used in courtship?
Two birds flying in synchrony, the more synchronous the display, the more likely birds are to mate
How are penguins adapted for “underwater flight”?
Increased weight to counteract buoyancy
Smaller wings for steering only
How do woodpeckers communicate?
Drum on tree bark
How do palm cockatoos communicate?
Use stick to drum on hollow branch
What structure do birds use to produce most of their sounds?
Syrinx
What structure do mammals use to make most of their sounds?
Larynx
What is the purpose of the larynx in birds?
Prevents food and water entering the respiratory tract
Where is the syrinx located?
Deep in the body cavity where the trachea branches into two primary bronchi
What structures surround the syrinx?
Clavicular air sac
Internal tympaniform membrane
How does the syrinx produce sounds?
When the clavicular air sac exerts pressure it pushes the internal tympaniform membrane into the syringeal passage, and when air flows through the syringeal passage the membrane vibrates
How much of air flow can the larynx convert into sound?
2%
How much of air flow can the syrinx convert into sound?
Up to 100%
How do canaries use the syrinx?
They sing with one side of the syrinx and breathe with the other - allows continuous singing
How do cowbirds use the syrinx?
They produce rapid notes alternatively from each side
How do thrushes use the syrinx?
Rising note from one side, falling note from the other
What are the two types of vocalisation?
Songs
Calls
Features of songs
Limited to passeriforms Often complex - long time, melodious Under influence of sex hormones Generally important in reproduction Usually makes produce song only
What are passeriforms? Examples?
Perching birds
Robins
Great tits
Nightingale
Why is there a “dawn chorus”?
Air stiller, so transmission good
Insects less easy to see/find so birds wouldn’t be feeding anyway
Many birds lay eggs in early morning
Good indication of quality of male if he is up early
Fewer predators
Features of calls
Most bird species use them
Acoustically simple
Not primarily sexual - both sexes use them
Purpose of calls
Warning of predator Indication of where food is Chicks call from inside eggs with temperature information Calls synchronise hatching Begging calls indicate hunger
In what species do chicks call from inside egg with temperature information?
Pelicans
What are the 4 functions of vocalisations?
Mate attraction (song)
Warning of danger (call)
Recruitment (call)
Territory defence (song)
Example of bird using song for mate attraction
Sedge warbler
Males arrive first from migration. Each male establishes territory in reed beds and sings complex songs to attract females returning from Africa
How do female sedge warblers pick a male?
They choose males with the biggest repertoires of songs
Example of bird using call to indicate danger
White-browed scrubwrens
Alarm call has more elements (trills) when threat is closer to communicate distance of predator
Scrubwrens more likely to flee when predator is nearby
Other species listen to alarm calls and also respond
What is the predator of scrubwrens and what does it do?
Pied currawong
Eats their eggs, nestlings, fledglings and adults
Example of using calls to recruit others
Pied babblers
Adults periodically give a ‘purr’ call which attracts others to a forage patch to share food
Call given you help independent fledglings who have trouble foraging by themselves
In what situation do pied babblers recruit fledglings to a good source and how do both groups benefit?
When adults find an abundant, divisible food source such as a termites nest
Fledglings gain foraging practice and success
Adults gain from increased survival of young - they may be relatives and a bigger group size means individuals are safer from predation
What are the 2 reasons recruitment calls are used?
To repel a predator with numbers or alert of a food source
What bird uses song for territory defence?
Great tits
Males establish woodland territories and sing once they’re settled
Variability in song complexity
How were territory defence songs studied?
Removal and playback experiments
Territories filled much quicker when there was no defensive song playing
Increased song complexity offered greater deterrancd
Do great tits respond faster to neighbours or strangers entering their territory and why?
Strangers - they present greater threat as they don’t have a territory of their own
What is the name for when a male and female bird sing together? Example of a bird that does this
Duetting
Australian magpie-larks
Their synchronicity increases the longer they spend together
Why do Australian magpie-larks sing together?
May be to defend territories
Male may be announcing that female is taken
What is the name for when all group members sing together?
Example of a bird species that does this
Chorusing
Kookaburras
Young birds rubbish - adults ‘laugh’ at them to teach them
