Birds Flashcards
What are the advantages of flight?
- Takes a 2 dimensional world and makes it 3 dimensional
- Provides access to virtually all environments around the world
- Ability to forage over large distances
- Ability to move to where the food is (nomadic species)
- Major long distance migrations (globally)
- Opportunistic breeding
- Ability to escape predators
Adaptations to enable flight?
Anatomical:
- Feathers & the shape of wing
- Musculoskeletal modifications
- Respiratory modifications
Physiological:
– Respiratory, Cardiovascular
– Energy metabolism
– Sensory
Behavioural
Functions of feathers
- Enable flight
- Thermal regulation
- Water proofing
- Camouflage
- Predator avoidance
- Sexual dimorphism
- Adult and immature plumage
Feathers wear out/Moult due to
Wear and tear UV light Soiling External parasites Old dead feathers fall out New living feathers grow in and then lose their blood supply and become inert
Patterns of moult
Once a year
Twice a year
Over multiple years
In orderly fashion or very extreme - waterfowl
How to birds protect against feather degradation?
Some birds have a Uropygial Gland - which is a oil gland located at the base of the tail which is spread of feathers by bird
Pneumatized bone in birds
- Skull, spinal cord
- Proximal bones in axial skeleton
- Sternum
- Directly connected to the respiratory tract
- All other bones contain marrow
Muscles in birds (enabling flight)
Different muscle types for different types of flight
•Types of flight:
Bursts
- Fast glycolytic fibres – fatigue easily only use glucose but generate more power
Acceleration and then continuous flight
Mixture of Fast oxidative Glycolytic fibres – oxidative (aerobic but also anaerobic – glucose) – efficient
Gliding flight
- Slow oxidative muscle fibres
- Slow but powerful, oxidative and slow to fatigue
- Found in the pectoral muscles of gliding flight
Respiratory system of birds
Upper Respiratory: Nares •Nasal passages •Infra-orbital sinuses •Cervicocephalic air sacs – Choana – Glottis •Is at the base of the tongue
Lower Respiratory: Trachea (Complete tracheal rings) –Syrinx –Source of the bird’s voice •Bronchi •Lungs •Air Sacs
Air sacs in birds
Transparent, like plastic wrap
•Paired cervicocephalic
–Subcutaneous
•Paired : intra coelomic
Two cycle respiration system in birds
First inhalation:
Passes through the lungs
- Result of caudal facing openings to the trachea
- Enters the caudal thoracic and abdominal air sacs
First exhalation:
Enters the lungs through the caudal facing openings in the trachea
Moves through the lungs via air capillaries
Second inhalation:
Air moves into the cranial thoracic and inter clavicular air sac.
Second exhalation:
Air moves from these air sacs into the trachea
Heart of bird
Four chambers
Almost axial position
Inverted electrical axis
Relatively large heart - increased stroke volume (flying requires fuel)
Oxygen delivery during flight
10-17x increase in O2 consumption
Cardiac output increases via increased heart rate
Increased density of capillaries in muscles
Haemoglobin in birds has low affinity for oxygen
Bird myoglobin has very high affinity for oxygen
How do Bar-headed geese which migrate at altitudes of up to 7250m respond to changes in O2 concentration?
Predominately with an increase in cardiac output
Mitochondria are closer to the capillary walls
Energy used by birds for flight
Short bursts = glycogen
Sustained flight = fat
Extreme circumstances e.g. migration or starvation = Protein
