lecture 3 avian adaptations chapters 4-6 in...

Lecture 3 Avian Adaptations

Chapters 4-6 in Gill

Why are birds birds?

Common Loon

Laysan Albatross

American White Pelican

Great Blue Heron

Roseate Spoonbill

Red-tailed Hawk

MN Volunteer 2006

Painted Bunting

Birds are Adapted for:

1. Weight reduction while retaining skeletal strength

2. Power3. Balance

Weight Reduction1. light skeleton relative to body

weight– hollow bones– reinforced

Weight Reduction2. networked bones3. truss-like structure - pectoral

girdle - a tripod of bones (scapula, coracoid, and clavicle)

Pectoral Girdle

Note: Responsible for terms in red

Weight Reduction

4. fusion of finger bones (metacarpals) - 2 missing and 2 fused, thumb supports the alula, wrist bones (carpals) reduced to 2

Wing and Alula

Weight Reduction5. reduction of tail to a pygostyle

Weight Reduction6. flattening of sternum - carina for

flight muscles

Birds are Adapted for:

1. Weight reduction while retaining skeletal strength

2. Power3. Balance

Balance Adaptations

1. center of gravity through reduced skull size and bulk just below the wings

2. fusion and elongation of pelvic girdle to support upper weight, but also for walking

Note how farback pelvic girdle is placed

Balance Adaptations

3. liver is on right to match single ovary on left

4. wide separation of legs to aid in egg-laying

5. general streamlining

Skeletal System1. Function

a. Supportb. Protection - e.g., of internal

organsc. Articulation - e.g., of musclesd. Manufacture of blood corpusclese. Calcium storage

Skeletal System

2. Modificationsa. Pectoral girdle

• scapula - thin, blade-like, long in strong fliers

• coracoid - stout bone• furcula - 2 clavicles (or wishbone)• sternum

Skeletal System2. Modifications

b. Pelvic girdle• Synsacrum• evolution toward fusion - early

archosaurian reptiles, pelvic bones radiate outward from acetabulumlike 3 spokes-ilium, ischium, and pubis

• long and narrow in walking birds• short and wide in flying birds

Pelvic Girdle

Note: Responsible for terms in red


c. Fused bones - especially in the hand and vertebrae


d. Sclerotic ring

Transverse Section Thru Eye

Skeletal System

2. Modificationse. Single condyle - provides greater

neck flexibility; some “hand”functions performed by the bill

f. Hyoid apparatus - allows great extension of the tongue in hummingbirds and woodpeckers e.g., up to 4x length of bill

Hyoid Apparatus

Northern Flicker


g. Vertebral column - vertebrae varies from 39 to 63

• most vertebrae are fused• ribs (double articulation) uncinate

processes increased support and strength both for flying and diving (e.g., loons the process extends across two adjoining ribs) - bones are "thin, flat"

Skeletal System

2. Modificationsh. Legs - femur is short and flat• tibia – drumstick• fibula - very small, splinter bone• tibiotarsus – the entire bone

including the tibia and proximal fused tarsal bones


i. Toes• Generally 4 toes• First is usually directed backward (hallux)

SkeletalSystem-

Legs

National Wildlife Federation –Award Winning Pictures –

2005?

Ancestral California Condor

lecture 3 avian adaptations chapters 4-6 in...

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