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Characteristics birds share with reptiles
- single occipital condyle
- single middlke ear bone
- lower jaw composed of five fused bones
- nucleated erythrocytes
- egg structure and egg tooth
- scales on leg (feathers also thought to be derived from scales)
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3 Types of Feathers:
- Contour Feathers: form the aerofoil (surface) of wings and tail. consists of a vane on either side of a shaft or rachis. vanes are made on barbs which are lined with barbules (have hooklets to make an interlocking flexible surface) they are impermeable to water especially when coated with water reppellant oil
- Down Feathers: lack barbules. are soft and fluffy. provide insulation
- Filoplume Feathers: ditributed through out the feathers. lack barbs and barbules. play sensory role allowing bird to feel the orientation of its feathers
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Support and Locomotion
- 5 classes of animals can fly/glide
- Powered Flight: the ability to gain altitude through muscularly controlled wing action (birds and bats only/ maybe flying fish)
- high degreee of skeletal and muscular adaptation for powered flight.
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Food Aquisistion and Digestion
- Birds are Voracious eaters
- there bills and tongues are modified to eat different types of food at different stages of their life and when food availability changes
- 3 types of bills:
- Crop: allows birds to ingest and store large quantities of food
- 2 parts of the stomach are also modified, the proventriculus (where gastric juices are secreted and the ventriculus or gizzard, which has muscular walls for crushing seeds and hard material
- granivorous (seed eating) birds eat small pebbles to help crush and grind up har matter in their gizzards.
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Gas Exchang and Water Balance
- lungs only have a single opening, and non bird lungs are less efficient than continuous flow because not all the used air is expelled during each breath (dead space=35% of luncg volume)
- modified bird lungs: extensive air sacs in most of the body allowing 2 cycle breathing
- no passage terminates blindly in the lung
- a syrinx supersedes the larynx as a vocal organ
- lungs of bird isolated in pleural cavities
- air sacs are blind thin walled distensible air sacs of the lungs, most birds have 5 or 6 pairs, they have poor vascular supply and no respiratory epithelia (no act in gas exchange)
- during flight they are rhythmically compressed to maintain constant flow over repsiratory epithelia, and play thermoregulatory role by dispelling heat produced during flight.
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2 cycle breathing
- inhalation - expansion of sac 2 (sac 1 already filled)
- exhalation - air sac 1 compresses refilling main lungs and continuing respiration
- inhalation - expansion of sac 1 (sac 2 already filled)
- exhalation - air sac 2 compresses refilling main lungs and continuing respiration
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Circulation
- Pectoral Arteries: unsually large to accomodate increased blood flow during activity
- Erythrocytes: are larege and bi concave to increase surface area. also allow oxyggen dissociation at high altitude to allow respiration
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Excretion
- birds secrete uric acid as a semi solid paste with the feces
- accomplished via their meta nephric kidney
- endothermy (thermo regulation/ homeostasis) requires a more efficient filtration system
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Sensory Abilities
- Vision: is an important sense for birds there fore they have large eyes
- Hearing: the dawn chorusis used when birds are defending a breeding territory or trying to attract a mate
- auditory and vidual cues are used to travel between breeding and wintering grounds (as well as magnetic)
- Olfaction: most birds dont use smell except for turkey vultures who locate prey largely by smell
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Reproduction
- seasonal developement of reproductive organs occur
- Males: testes increase 300 fold
- Females: left ovary and oviduct develop at maturity
- Purpose of seasonal adaptations: minimize energy investment, and restric behavioural influences of the hormones they are subjected to during mating season
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