Birds

Adaptations for flight

• Wings

• Feathers

• Streamlined Body

• Light, pneumatic bones (hollow)

• Centralised internal organs, centralising helps faster metabolism and save weight

• Rapid metabolism

• Small braincase & brains - efficient brains highly cognitive. reduce excessive baggage

• No urinary bladder

• efficient breathing system with the air sacs that you don’t mix oxygen and deoxygen

types of flight

Flapping

• Up and down wing beats using lift and thrust ****

Gliding

• usually large birds, once flapped out into the air, extend their wings and can coast forward. large birds mass helps them overcome air resistance. can be efficient but loose altitude. 20M forwards for every 1M of altitude lost

Soaring

• used by very large birds like large seabirds of eagles and allows them to stay airbourne with minimum energy use. They use rising air currents either from the sea or updrafts or thermals from the cliffs. wind gradients of the oceans, thermals off the land, or updraft on hills and cliffs

Hovering

• very energy intensive, only do it for short periods. rapid flapping. humminbirds is only bird that can do sustained flappping due to nectars very high energy source. have high adaptations to feed on the nector and muscle strength.

Feather structure

• crucial for flight

• thermoregulation

• display

• pennaceous part (distal section of vane)

  • Firm, compact

  • Provides airfoil

  • protects body from moisture and injury

  • provides colors & shapes for display

• Plumulaceous (Proximal section of vane)

  • ****soft, downy

  • provides insulation

Made of keratin - have had the same developmental pathway as other reptillia like snakes and turtles. they come from the epidermis and dermis and skin, same type of development but take very different form.

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Types of feathers

Semiplumes

downy (soft), fill function between the contour & down feathers. provide insulation and maintain smoothness of plumage

Down Feathers

soft fluffy feathers, lack interlocking barbules. baby birds also waterproofing. for excellent insulation

Bristles

stiff shafts with barbules, proximal section. Base of bill & around eyes. round eyes and around bills. sensory function, and protects eyes

Filoplumes

very fine shaft with a few short barbs at the end. function as pressure & vibration receptors. use them to adjust other feathers for both insulation and aerodynamics

endothermy

• Maintain & regulate high body temperatures (up to 40 degrees celcius)

• High rate of metabolism

• Heat produced mainly visceral organs

• Mechanisms controlling heat loss

  • Raising & flattening feathers, they lay feathers flat against their skin to stop heat escaping or raise them to let heat out. allows air circulation to squeeze out

  • Shivering - generates heat when cold

  • Panting - generate heat loss when hot

  • Fat layers - maintain heat loss in cold areas

evolutionary traits of modern birds

• Lack of teeth, have the tough beak instead that they can bang into food like seeds without tooth breakages. takes away the weight

• Lack of tail (save weight)

• Not pre-tertiary birds had these

Skeletal adaptations

• Sternum (keel in flighted birds), only in flighted birds

• Fused skull - stability and reduces weight

• Fused bones in hind legs (tibiotarsus and tarsometatarsus), provides strength and stability when landing, swimming.

• Strong pelvis - impacts of landing and lots of them perch and walking strenght

• Strong bones perforated with air sacs, hollow bones

• fused and flattened wing bones (carpo and metacarpos)

most adaptations present to help reduce the weight of the birds

Chambered Heart

• Birds have 4-chambered heart

  • 2 atria & 2 ventricles

  • helps to increase efficency, better for faster metabolic rate

• Extra ventricle allows deoxygenated blood to be pumped separately to lungs and body - more efficient. right ventricle - lungs, left ventricle - body

respiratory system

• very small lungs

• air sacs in front and behind the lungs

• They are so massive they can enter major bones like the humerous through teh holes in the top end

• birds need to breath twice

1. first inhilation - air goes to the prosterior air sac (air going one way)

2. breath out - air goes to the lungs, this is where oxygen within the parabronchi in the lungs, that’s where oxygen exchange occurs

3. parabronchi is specialised structure which allows oxygen to diffuse into the blood stream

4. inhale again and inspire again, this time air goes into the anterior air sac

5. when we breath out the deoxygenated air leaves the bird

digestion

Crop

• sorts out hard & indigestible food. gathers the food in quidckly and allows the bird to regurgidate that

Proventriculus

• Mixes food with acidic secretions

Gizzard (stomach teeth)

• very hard Muscular organ lined with keratin , stones grind up food. uses small stones (grit). If they don’t ingest the grit into the gizzard theres’s a 50% decrease in digestion efficiency

Intestine

• absorption

cloaca

• One hole, gets rid of all digestive waste. They have uric waste. dont’ have urinary bladder to remove uneccesary weight of the liquid

First proper bird

Archaeopteryx lithographica,

• had fused clavicle

things that birds don’t have

• tail

• teeth

• no sternum - has thin gastri ribs instead

• small coracoids (in modern birds they are large and critical for stabilising flight muscles)

microraptor from china

• seemed to have wings on both forelimbs and hindlimbs

feathers apparent on many without wings so thought to of been used for endothermy first before anything

hypothesis evolution of flight

Ground up

Initially cursorial - were running fast animals which needed to catch insects etc. so feathers intiially involved for insulation or display. helped them leap into the air

Trees/cliffs down

they were boil dinosaurs, formed modifications that allowed them to gluide (like flying squirils) but overtime could produce fligth

Bird types

Flightless birds (ratites)

Raptors (Accipitriformes)

Parrots (order:psittaciformes)

Passerines (Order:passeriformes)

Penguis (sphenisciformes)

Flightless birds (Ratites - Running Birds)

• flightless birds (running birds)

• no keel, highly modified skulls (paleonatus skulls)

• Gondwanan

• large bodied and has very large egg

• in austrlia - emus and cassowary

• built very strong legs

• often father looks after chics

• in NZ - kiwi, used to have moa,

• south america and south africa - ostrich

Raptors (Accipitriformes)

• Carnivorous birds

• Strong legs with raptorial claws - opposable tearing flesh

• Broad wings for soaring

• Hooked beak tearing flesh

• eagles hawks owls

Parrots (order: Psittaciformes)

• Likely Gondwanan origin

• Strong, curved bill, an upright stance, strong legs & clawed zygodactyl feet (2 toes facing forward, 2 toes facing backwards)

• Highly intelligen

• Many use tools

• capable of mimicry

• often colourful

Passerines (Perching Birds, Order: Passeriformes)

• more than half of the world’s bird species

• Perching feet, dactyl arrangement - 3 toes forward 1 toe back

• Many produce great songs (songbirds)

• Gondwanan origin

Penguis ( Order: Sphenisciformes)

• Aquatic fish feeders, fish squid and other marine prey

• Wings modified into flippers

• Thick insulating feathers

• Can drink salt water specialised glands that secretes salt

• Mostly southern hemisphere (1 in galapagos crosses north)