1. Aves (Birds)

2. Characteristics Over 9900 species
Outnumber all other vertebrates except fishes
Single unique feature set apart birds from other animals
Feathers - If it has feathers it’s a bird
Entire anatomy is designed around flight
Wings for support & propulsion
Bones rigid, light, & hollow
Highly efficient respiratory system
High-pressure circulatory system
Finely tuned nervous system

3. Living Birds Two groups Palaeognathae Neognathae
Large, flightless ostrich-like birds & kiwis
Flat sternum & poorly developed pectoral muscles
Neognathae
Flying birds with a keeled sternum where flight muscles attach

6. Feathers
The most distinct characteristic of birds is the presence of feathers.
Feathers have multiple purposes, including enabling flight.
Develop from follicles in the skin
generally arranged in tracts (or pterylae), which are separated by patches of bare skin (the apteria).
Some species, such as penguins, lack pterylae and instead the feathers are uniformly distributed over the skin.

8. Feather Parts
Feathers are anchored in the skin by a short, tubular base, the calamus
remains firmly implanted within the follicle until molt occurs.
Barbs
closely spaced side branches
Barbules
branch from the barbs, and proximal and distal barbules branch from opposite sides of the barbules.
Ends of the distal barbules have hooks that insert into the grooves of proximal barbules of the adjacent barb.
hooks and grooves act like Velcro to hold adjacent barbs together, forming a flexible vane.

10. Electron microscope image of a body-contour feather that shows the barbs, and how barbules on adjacent barbs Velcro together.
When barbs and barbules are stiff and held tightly together, the feathers together form a tight, sheet-like, surface = Pennaceous texture
When barbs are flexible and the barbules lack hooks, the feather has a soft, loose, fluffy texture = plumulaceous texture

11. Skeleton Pneumatized bones Skulls Horny (keratinous) beak
Light, delicate, laced with air cavities, & strong
Skulls
Built light & mostly fused into one piece
kinetic
Horny (keratinous) beak
toothless

12. Skeleton Vertebrae fused together; Bones of forelimbs Sternum
ribs are mostly fused with vertebrae, pectoral girdle, & sternum
Promotes rigidity
Bones of forelimbs
Modified for flight
Reduced in number
Several fused together
Sternum
Bears a large, thin keel to provide muscle attachment

14. Muscular System Muscles are relatively massive
Largest is the pectoralis
Depresses the wings in flight
Supracoracoideus is the antagonist muscle
Creates a rope-and-pulley system

15. Digestive System Insects the largest component of the diet
Grinding of food occur in the gizzard
Lack teeth
Short pharynx
Long, muscular, elastic esophagus
Many birds have an enlargement at the lower end (crop) that acts as a storage chamber
Stomach
Proventriculus – secretes gastric juice
Gizzard – grinds food
Intestines
Cloaca – terminal part
Also receives genital ducts & ureters

17. Circulatory System Respiratory System 4-chambered heart
Strong ventricular walls
Heartbeat is extremely fast
Respiratory System
Parabronchi
Ends of bronchi which air flows continuously
Extensive system of nine interconnecting air sacs

20. Nervous & Sensory System
Well-developed brain
Cerebral hemispheres, cerebellum, & optic lobes
Relatively intelligent birds (crows & parrots) have larger cerebral hemispheres then less intelligent birds (chickens & pigeons)
Cerebellum – coordinates muscles, equilibrium
Optic lobes – form a visual apparatus

21. Flight a balance between two sets of forces
lift and weight, and thrust and drag
Weight is the result of gravity and is reduced as much as possible in birds (anatomy).
Lift is generated by the flow of air over the wings.

22. Basic Forms of Wings Elliptical Wings
most small forest and scrub-dwelling birds, such as robins and sparrows
Low aspect ratio
Ratio of length to average width
These wings allow a high degree of control and manoeuvrability in confined spaces
minimize drag to allow rapid ascent and descent
Wing beat is usually rapid
highly slotted between the primary feathers
helps to prevent stalling during sharp turns, low-speed flight, and frequent landing and takeoff.

23. Basic Forms of Wings High speed wings
found on swallows, falcons, shore birds, and ducks
Birds that feed on the wing or make long migrations.
bones are relatively long, wings taper to a point to allow for high flight speed with low drag, and low energy consumption during flight.
wings are also thin
must be flapped for short glides and during descent, and flaps are fairly rapid but small.
aerodynamically efficient for high-speed flight
Cannot keep a bird airborne at low speeds.

24. Basic Forms of Wings Long soaring wings
found on terns, albatrosses, gannets, frigate birds, gulls and other sea birds.
high aspect ratio resembling those of sailplanes.
open spaces allow for long wings to create good lift with little energy expenditure.
adapted for high speed and dynamic soaring
less manoeuvrable than the wide, slotted wings of land soarers
Birds can glide easily over large expanses of water and have exploited the sea winds
birds must usually run and take off into the wind to get off the ground, and usually land easily on water.

25. Basic Forms of Wings High-lift/Broad soaring wings
found on vultures, condors, hawks, ospreys, pelicans and eagles
wings are broad and only relatively long
takeoff and landing in fairly confined areas, high lift, low speed soaring, and slow descents.
Many of these birds are land soarers
good manoeuvrability required for tactic soaring in the air currents over land.