birds – part ii vertebrate zoology (vz lecture24 – spring 2012 althoff - reference pjh chapters...
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Birds – Part II
VERTEBRATE ZOOLOGY (VZ Lecture24 – Spring 2012 Althoff - reference PJH Chapters 16-17)
Bill Horn
Body Form and Skeleton
• Feathers: molded for aerodynamic forces; light, strong…very resilient for their weight
• Skeleton: a) skull is remarkably light b) wing bones air filled c) leg bones heavier than
same-sized mammal *overall:
more mass is concentrated in____________ than comparable sized
mammals
Body organ “reductions”
• Birds ______ urinary bladders
• Most birds have only one ovary (or only one _______________ ovary)
• _________ of both sexes are usually small (with hypertrophy or regression depending on time of year)
Muscle & Cardiovascular Output
• Pectoral muscles (major wing muscles-downstroke) may account for ______ of total body mass of strong fliers
--power output per unit of mass for dove estimated to be 10-20x
that of most mammalia muscles• _______ heart and high rates of blood flow coupled
with complex lungs that a) maximize gas exchange
b) dissipate heat produced by high levels of muscular activity during flight
FAVEOLARLUNG
Streamlining
• Birds _____ vertebrates that move fast enough for wind resistance and streamlining to be important
• “Fast birds”songbirds: up to 50 km per hour
ducks & geese: up to 80-90 km per hour peregrine falcon: 200 km per hour in dive
Structural characteristics like fast-flying aircraft: ______________ make smooth joints between wings and body, and head and body ___________ close to body in flight
Not-so-streamlined
• Some birds are slow fliers….slow to launch into flight, slow in-flight
• “Slow birds”spoonbills
flamingosherons
cranes Structural characteristics opposite of fast-flying
aircraft: long-legged with legs that trail behind and/or
not tucked up under the body long-necks extended
Air-filled bones…fused and thinner bones
• Also referred to as ____________ bones• Not present in all birds• Better developed in larger birds than smaller birds• Diving birds (penguins, grebes, and loons) have
little pneumaticity in their bones• Skeletons of most birds exhibit some pneumaticity
in pectoral girdle and humerous• Pelvic girdle: elongated with ischium and ilium
broader and much thinner than ancestral reptile line….and combined with the synsacrum—a fusion of 10-23 vertebrate…. pygostyle—fused caudal vertebrate
Fusion of vertebrae means more rigidity
• Overall, reduction in number of vertebrae and fusion of vertebrae…and relatively immobile thoraic vertebrae…in combination with elongated, “roof-like” pelvis produce a nearly RIGID vertebral column.
• The rigid “trunk” is balanced on the legs• Femur projects to the anterior…combined with
articulation of with the tibiotarsus and fibula results in this being the bird’s center of gravity
center
of
gravity
Other “skeleton” features of note….• Wings positioned above the center of gravity• Sternum greatly enlarged (most with keels…as
noted) for greater amount of surface area• Scapula extends posteriorly above ribs and is
supported by coracoid which is fused ventrally to the sternum
• Clavicles project to anterior—usually fused to form the furcula (wishbone)… provides additional bracing
• Hind foot typically greatly elongated with ankle joing within the tarsals
• Tarsometatarsusmetatarsals of some toes fused with the distal tarsals
• Tibiotarsustibia fused with proximal tarsal bones
Muscles – Mass distribution differences
• Hummingbirds & swallows
mostly flight
• Predatory birds flight but use
legs to capture prey
• Swimming birds
• “Terrestrial” birds--run
instead of fly to flee
flight muscles ________ of
total body mass, legs _____
flight muscles ~_____ of
total body mass, leg _____
limb & flight muscles about
equal percentage, overall
_______ of total body mass
limb muscle mass ___ than
flight muscle mass
Muscles • Two basic processes “fuel” muscle contract:
a) ____________ metabolic pathways--achieve “quick” response --does not requires O2 --more fast-twitch muscle fibers, relative
to slow-twitch muscle fibersb) ___________ metabolic pathways
--achieve “sustained” response--requires O2 --more slow-twitch muscle fibers, relative
to fast-twitch muscle fibers--slow-twitch muscle fibers contain lots of
_____________
Fast vs. Slow Twitch Muscle Fibers
Category Slow-Twitch Fast-Twitch_____________ more fewer_____________ more lessMyoglobin more lessColor appearance red-brown white____________ build-up lower higherFatigue slower quicker
Muscles & Birds Other “flier” vs. “runner” differences
• Composition of leg muscles indicates regular, sustainable activity
• Composition of breast muscles (major muscle groups responsible for up- and downstroke of wings) indicative to long vs. short flight capabilities
• Fliers—(think songbirds, waterfowl, etc.) a) legs: large amounts of myoglobin b) breast: large amounts of myoglobin
• Runners—(think quail, pheasant, wild turkey)a) legs: large amounts of myoglobin
b) breast: essentially lack myoglobin
Major Flight Muscles
↓ __________________ – origin on keel of sternum (lateral side) and inserts at humerus on
ventral sidecontracts for ______________relaxes during upstroke
↑ _________________ – origin on keel of sternum (lateral side), passes through foramen
triosseum, inserts (tendon) on dorsal head of humerus. Foramen trosseum formed by articulation of the furcula, coracoid, and
scapula.relaxes during downstrokecontracts for ______________
pectoralis
supracoracoideus
__________________
right humerus
Left humerusForamen
triosseum
Major Feather Types on the Wing
Primaries (remiges = wing feathers)
Secondaries (remiges = wing feathers)
Major coverts – leading edge of wing
Alula—forms wing slot on leading edge (at carpal bones
Major Feather Types on the Wing
Fig. 17-8 p444, PJH