Flight and feathers

150 million years ago

• went from a reptilian ancestor into feathered birds

• not great flyers

• first diversified in the mesozoic

• diversified more in the tertiary

  • more modern taxa

extinctions

• Class Aves was in several extinctions

  • late cretaceous

  • pre-pleistocene ice ages

    • 25% of existing birds lost

birds as reptiles: commonalities (5)

• skull holds a lot of the similarities

• similar leg structure

• scales

  • feather are modified scales

  • scales are on bird legs

• females are heterogametic

• nucleated red blood cells

birds skulls as compared to reptiles

• lower jaw composed on several bones

• ring that supports the eye

• single middle ear bone

• single occipital condyle

• lower jaw articulated on quadrate bone

• expanded lateral brain case

archaeopteryx

• the original link between birds and reptiles

• a find so good that people thought it was fake

• came out briefly after Origin of Species

• found in fine-grained limestone in central europe

  • late jurassic

• first evidence was a single feather

• that cool as skeleton was found, second

• feathers are indistinguishable from modern feathers

Newer fossil finds

• seven specimens

• Crow-sized, bipedal ‘reptile’

• Blunt snout, many small teeth

• Feathers on wings and tail (probably entire body as well)

• Capable of gliding, weak flapping

• Feather veins were asymmetric

  • Indication of flight

archaeopteryx as a intermediate

• similar features

  • skeletal, brain, inner ear

• brain 3x larger than comparable reptiles

  • smaller than modern birds, birds have much larger brain than reptiles

  • larger visual centers

    • good for hanging out in the air

  • neural system for flight

• heavy skull

  • boney, teeth

  • enhances inner ear structure

• has claws 

• long, boney tail

• overall, heavy for a bird

birds as dinosaurs

• the line of evolution is debated

  • thecodonts vs theropods 

    • theropods is the more accepted opinion

    • are related to trex

birds as dinosaurs - sinornis santensis

• china 1987

• toothed cretaceous fossil

• sparrow sized

• halfway point between ancient and modern

• many intermediate features between Archaopteryx and modern birds

  • Strong hand, forearm, and pectoral girdle modifications

    • bones are starting to fuse

    • rigidity of the skeleton

  • Raise wing over body

  • Large pygostyle –tail support

    • goodbye tail bone!

  • Opposable rear toe

    • good for perching

birds as dinosours - feather development

• birds are in fact related to t-rexes

  • fully feathered dinosaurs 

  • onset of downy feathers

  • good for thermoregulation 

keel bone

• important for flight muscles

• scapula looking abdonmen bone

feathers are skin structures

• provide insulation, aerodynamic for flight, color for communication and camouflage

• modified feathers

  • swimming, sound production, hear, protection, cleanliness, water repellency, water transport, tactile sensation, support

beta-kertain

• fibrous protein polymer

• unique to reptiles and birds

• makes up feathers

contour feather

• long central shaft

  • calmus and rachis

• broad flat vane on either side

calamus

anchors feather in follicle below skin surface

rachis

supports vein

barbs

• lateral branches off of rachis

• primary elements to the vane

• ramus

• barbs and barbules form an interlocking but flexible planer surface

ramus

• barbuels 

• tapered central axis with smaller barbules projecting from both sides

• barbules consist of a series of single cells linked end to end

• can be simple or have projections

  • barbicels

  • hooklike

grading contour feathers

• hidden, fluffy basal part

  • insulation

• exposed cohesive outer part

  • variety of functions

• difference?

  • the lack of barbules towards the base

vaned feathers

• most conspicuous

• smaller contour feathers

• flight feathers

• smooth overlapping arrangement

  • reduces turbulence

wing feathers componants

remiges, coverts

remiges

• large, stuff, pennaceous

• primaries

• secondaries

reminges - primaries

• outer, distal feathers

• forward thrust

• vane location is asymmetrical

• most birds have 10 primaires

• flight efficiency is related to primary structure

• next to 0 modifications

remiges - secondaries

• inner, proximal

  • closer to the body of the bird

• vane location is symmetrical

• 10-19, 40 in albatross

• major structural modifications are more prevalent 

coverts

• overlap remiges 

  • reduces drag

• covering gaps between feather

tail feathers - rectrices

• turning

• symmetrical vane location

• 12 rectrices

  • 6L and 6R

• essential feathers

  • deck feathers

  • central feathers

• major modifications more prevalent

down feathers

• soft, fluffy

• thermal insulation

• lack rachis

• trap air next to skin

• semiplumes

• filoplumes

• bristles

• powder downs

down feathers - semiplimes

• intermediate structures between down and contour feathers

  • enhance insulation

  • fill out aerodynamic contours of body plumage

  • courtship ornaments

down feathers - filoplumes

• hairlike

• monitor movement and position of adjacent vaned feathers

  • allows them to hover in the air during hunting

• distributed throughout plumage

• numerous near mechanically active areas

  • flight feathers

    • 8-12 filoplumes each

    • at the base of the feathers

• consists of a fine rachis that thickens distally

  • ends in terminal tuft of barbs w/ barbules 

down feathers - bristles

• specialized feathers with sensory and protective functions

• stiff tapered rachis

  • few basal barbs

• on heads of birds

• raptor

  • simplified so that they’re easier to clean

• Also occur as eyelashes in rheas, cuckoos- nostril covering in woodpeckers, jays, crows- around mouth in most aerial insect-eating birds for sensory information 

down feathers - powder downs

• produce dust-like keratin 1 micrometer in diameter

• dispersed throughout feather coat

• found in herons, cockatoos 

• disputed in function

  • waterproofing?

  • Parasite prevention?

feather growth

• feathers are dead structures

  • after fully grown

    • cannot change color or form

    • can fade or be abrated 

  • mechanisms for damage repair

    • replace the feather