Characters of Birds--more uniform in characteristics than mammals - partly due to selection for flight
1. Feathers: 2 primary functions (Pp. 421-425)
A. insulation - traps air space
B. light-weight air foils for flight (Fig. 15-8)
C. secondary functions: display, sensory,
protection
2. Skeletal Modifications (Fig. 15-17)
A. bipedal
B. pneumatic bones--thin, hollow bones (Fig. 15-16)
feathers may weigh more than skeleton.
C. loss of teeth & heavy jaws replaced by
horny beak—lighter (Fig. 16-1)
D. loss of tail: no caudal vertebrae
E. furcula - fused clavicles, only in birds
"wishbone" (Fig. 15-13)
3. Reproduction
A. all birds are oviparous - amniote egg
B. sophisticated behavior associated with
courtship, mating, nest construction, and raising of the young
4. Excretory System
Excrete uric acid--requires less H2O for storage than ammonia (NH3) or Urea CO(NH2)2
Birds have no urinary bladder
Metabolic waste secreted as uric acid--C5H4N4O3
5. Physiology
A. birds are endothermic--maintain a constant body temperature. 40C
B. high metabolic rate--to cope with high
energy cost of flight
6. Circulatory System
A. 4-chambered hear
B. nucleated red blood cells--as in all lower
vertebrates
7. Respiratory System (Pp. 434-435)
A. well developed lungs, one-way air flow
system
B. Air sacs connected to lungs reduces the density of birds and cools the animals, especially during flight. These are well developed in good fliers; they even enter spaces in long bones.
Flow of air through avain lungs and air sacs:
posterior Fig. 15-19
air sac
to Cross-current exchange
lung Fig. 15-20
to
anterior
air sac
Because of cross-current exchange in lungs, blood leaving the lungs has higher O2 than exhaled air.
8. Nervous System
A. well developed brain - relatively intelligent
B. well developed optic lobes--sight is the most important sense for birds. An exception is the oil bird of South America which lives in caves and is the only bird that echolocates.
Origin of Feathers
Feathers: a unique avian character. The original function of feathers was probably insulation, later modified into flight feathers.
Feathers are derived from scales; the early development of a reptile scale and bird feather is identical.
Feathers are made primarily of beta keratin, as are reptile scales and mammalian hair.
Origin of Flight
Flight has evolved independently in arthropods, pterosaurs, birds, bats.
Two hypotheses for origin of bird flight
A. Arboreal
"Proavis" may have lived in trees; Archeaopteryx had perching foot, claws on wings for climbing like young hoatzins.
"Proavis" may have parachuted from trees to escape predators.
Feathers original function was insulation, but aided in gliding.
Flight evolved after gliding.
B. Cursorial
"Proavis" may have been a ground-living bipedal animal. Feathers already existed for insulation. Proavis used its arms with long feathers as an insect "net". Flapping of "wings" aided animal in its leaps to obtain food. Subsequently, powered flight was perfected.
In both models, Proavis was an active, warm-
blooded, feathered, bipedal animal.
CLASS AVES
Birds as feathered dinosaurs (Pp. 410-412)
The text discusses some recent fossil finds from China that include some remarkable feathered dinosaurs (Dromeosaurs: including Caudipteryx, Protarchaeopteryx, and Sinosaurapteryx).
Avian Systematics: Table 15-1
A. SUBCLASS ARCHAEORNITHES ("Old Birds")
· Presently contains only Archaeopteryx Fig. 15-2.
· Fossils from Jurassic Period--Bavaria
· Characters of Archaeopteryx:
1. Teeth present.
2. Claws on wing. Only living bird with this is the hoatzin in which the young birds use them for climbing.
3. Hands reduced to 3 digits = synapomorphy with coelurosaurs.
3. Caudal vertebrae (tail) present.
4. Keel on sternum not large.
5. Solid bones.
6. furcula (fused clavicles) present, as in modern birds = synapomorphy with coelurosaurs.
7. feathers
B. SUBCLASS NEORNITHES ("New Birds")
Superorder Paleognathae: mostly flightless birds that live primarily on Southern Continents, called ratites
Characters:
1. Absence of flight feathers.
2. Reduced keel on sternum.
3. Arrangement of bones of palate is the same as in Archaeaornithes.
· Elephant birds (extinct): Africa; 3m tall weighed over 1,000 pounds, 20 lb. egg--2 gal.
· Moas (extinct): New Zealand; several species, with the largest reaching over 12'
· Ostrich: largest living bird; lives in Africa; eats plants and small animals
· Emu: lives in Australia and reaches 6'
· Cassowary: lives in Australia & New Guinea
· Kiwi: 3 species that live in New Zealand
· Rhea: South America
· Tinamous: only group of ratites that fly, found in South America, Central America, and Mexico
Superorder Neognathae: All other living birds
About 22 orders, of which you should know the following:
· Order Podicipediformes: grebes; 1 family (aquatic fish-eaters): western grebe, horned grebe
· Order Anseriformes: waterfowl 2 families, including ducks, geese, and swans: mallard, Canad goose, trumpeter swan
· Order Pelicaniformes: marine birds; 6 families, including pelicans, cormorants, anhingas, frigate birds (primarily marine fish-eaters): white pelican, double crested cormorant
· Order Ciconiiformes: wading birds; 7 families: egrets, herons, ibises and storks: cattle egret, snowy egret, little blue heron, roseate spoonbill, flamingo
· Order Falconiformes: birds of prey; 5 families, including vultures, hawks, eagles, and falcons: sparrow hawk, goshawk, griffon vulture, king vulture, osprey, harpy eagle
· Order Galliformes: fowl; 7 families, including the chicken, turkey, grouse, and pheasants: turkey, sage grouse, blue grouse, Gambel’s quail
· Order Gruiformes: 12 families, including cranes, coots,rails and the fossils Phorusrhacus and Diatryma (Terror crane; Fig 16-2): sand hill crane
· Order Charadriiformes: shorebirds; 16 families, including plovers, sandpipers, gulls, terns, and skimmers: California gull, ring-billed gull, piping plover, kildeer
· Order Gaviiformes: loons; 1 family (aquatic fish-eaters): Pacific loon
· Order Columbiformes: 3 families, including pigeons, doves, and the recently extinct dodo: spotted dove
· Order Psittaciformes: parrots and macaws; 1 family (wild-caught cage-birds often infected with Newcastle's Disease, which can infect poultry): scarlet macaw, greenwing & hyacinth macaws, blue and gold macaw
· Order Strigiformes: owls; 2 families: saw-whet owl, snowy owl
· Order Apodiformes: hummingbirds and swifts; 3 families (extremely high metabolism during flight; torpor at rest): Anna’s hummingbird, broad-billed hummingbird, Rivoli’s hummingbird
· Order Piciformes: woodpeckers and toucans; 6 families: downy woodpecker, red bellied woodpecker, pileated woodpecker, flicker
· Order Passeriformes: perching birds/songbirds; 64 families including larks, swallows, wrens, blackbirds, thrushes, robins, mockingbirds, etc.; comprise about 1/2 of all species of birds, and since passerines are monogamous, this is a major reason why "most birds are monogamous": bluebird male, bluebird female, cardinal, bluejay, hooded oriole, cedar waxwing