Ornithology

Basic Characteristics, Evolution of Birds, Form and Function,

Intro/Basic Characteristics

What are birds?

• Taxonomy– Kingdom Animalia

• Phylum Chordata– Class Aves

Characteristics

• Bipedal

• Feathers (diagnostic)– Insulation– Lift and thrust

• Toothless bills covered with horny sheath

• Wings

• Ability to fly*

Characteristics (cont.)

• Adaptations associated with flight:

– Skeleton– Musculature– Physiology– Reproductive system– CNS– etc…

Adaptive Radiations (within adaptive radiations)

• Evolution of ecological diversity within a rapidly multiplying lineage (Schluter, 2000)

• 150-160 MYA

• >10,000 species extant– Fraction of what has existed

Ur bird ancestor

Hawaiian Honeycreepers

• Radiations within smaller groups

• Radiation in body parts

A note on Avian Classification

• Imprint of Linneaus 1758– Binomial nomenclature

• Upupa epops

– Standard English Names (“Common Name”)

– In NA, both established by AOU

Genus species

KingdomPhylumClassOrderFromGenusspecies

Classification of three species of woodpeckers

Taxon Downy Woodpecker Hairy Woodpecker Northern Flicker

Class Aves Aves Aves

Order Piciformes Piciformes Piciformes

Family Picidae Picidae Picidae

Genus Picoides Picoides Colaptes

Species pubescens villosus auratus

Current Classification

• 29 orders

• 187 Families

• 2000+ Genera

• 10000+ species

• Rapidly changing

Interesting biogeograpy• Each faunal region

has its characteristic birds – endemics

Biogeography (cont.)Regions Endemic (non-passerines) Representative Family Radiation

Holarctic

Incl. Nearctic and Palearctic

Loons, (Gaviidae)

Auks (Alcidae)

Accentors (Prunellidae)

NW warblers (Parulidae)

OW warblers (Sylviidae)

Neotropical Rheas (Rheidae)

Sunbittern (Eurypygidae)

Motmots (Momotidae)

Hummingbirds (Trochilidae)

Tyrant-flycatchers (Tyrannidae)

Ethiopian Ostrich (Struthionidae)

Turacos (Musophagidae)

Woodhoopoes (Phoeniculidae)

Larks (Alaudidae)

Sunbirds (Nectariniidae)

Oriental None Leafbirds (Irenidae)

Pheasants (Phasianidae)

Flowerpeckers (Dicaeidae)

Australasian Emus (Dromiceidae)

Kiwis (Apterygidae)

Monarch-flycatchers (Monarchidae)

Birds-of-paradise (Paradisaeidae)

Biogeography (cont.)

• Most bird communities or faunas are mosaics of species of various ages from various historical backgrounds

• + factors affecting species richness

LocalBird Community

RegionalBird Community

Speciation

Mass extinction events

Habitat selection

Immigration / Invasion Stochastic extinction events

Competitive exclusion

Predatory exclusion

From Ricklefs and Miller, 2000

1998

Evolution of Birds

Note on Phylogenetics

• Phylogenetics – History of the evolution of a group• Cladistics – defining groups based on shared

characteristics not found in ancestors (derived)• Cladogram – “tree-like” hypothesis of the hierarchical

evolutionary relationships of a groupA

B

C D E

time

FOTUsTipsNodesBranchesExtinct taxaSpeciation“Reading” the tree

Based on shared, derived characteristics

middle ear bones

Diversity of Birds100,000 species!

• Due to :1. Phyletic evolution

2. Cladistic evolution (speciation)

3. Extinction – “termination of a lineage”

a

b

c

Tim

e

a

b c

a

b a b c

a

d

- Heritable variation in a population due to mutation

- Some variation leads to differential reproductive success (if expressed)

Pg 47

Shared, derived characters with anything?

Other features?

• Nucleated RBCs• Scales• Ankle in tarsal bones (not between long

bones and tarsals)• Bipedal (theropods)• Yolked, polar, cleidoic egg• Females are heterogametic• etc…

Link Between Birds and Reptiles

• Lots of morphological, behavioral and physiological similarity between Reptiles and Birds.

• Which reptiles???

Founding of Archaeopteryx

• Lithograph Quarrymen – Jurassic limestone • Single feather impression – 1861, Bavarian

Quarry• Complete skeletal impression – Few months

later• 2nd complete skeleton – 1877, quarry near

Eichstatt, Germany

• Herman von Meyer– Archaeopteryx lithographica

Archaeopteryx

• Debates

– Support of Darwinian evolution• Darwin predicted transitional fossils in 1859• ‘one of the best links between two taxa’ (Feduccia, Ostrom, etc.)

– Creation / Evolution debate (pg 27)

– Evolution of feathers (flight or insulation first?)

– Evolution of homeothermy in birds

– Evolution of flight• Ground-up vs. Trees down

Could it fly?

The ‘historical’ evolution of flight debate

• Two main hypotheses:– Ground-up (cursorial hypothesis)– Trees-down (arboreal hypothesis)

Ground-up

• Assume biped, cursorial ancestor

• Has to be bipedal to use wings at all

• Large legs for running muscle attachment

• Bones of legs are long

• Once running:– Use feathers for other things

• Catch insects• Pick up minimum speed for lift: Flight

Trees-down

• Assume semi-bipedal leaping and gliding ancestor

• Use of claws to scale trees, then glide to ground• Claws retained in winged appendages• Short hand wing (power), relatively long arm

wing (lift)• Claw geometry (Feduccia’s study)• Large attachment sites for downstroke on

humerus but no keeled sternum• Flying squirrels?

Winner?

• Trees-down…maybe• Largely historical debate

• More productive???– Why evolve flight?

(1) To help escape from predators (2) To help catch flying or speedy prey(3) To help move from place to place (leaping or gliding)

• Vigilence• Migration, etc…• Nomadism

(4) To free the hindlegs for use as weapons

Craniate phylogenyand diversity of living speciesFrom Bemishttp://www.bio.umass.edu/biology/bemis

1/31/06

• Lab tomorrow – in the field (Briar Creek Lake)– Bring

• Clothes• Binoculars• Waterproof notebook• Time to meet?• Lab Activities BWSV• Read Taking Field Notes Handout

– Lecture Today• End Evolution• Start Form and Function

– Feathers

Fig. 3.25

Fig. 3.20

Alternative Hypotheses?

• Overhead from Feduccia

Leading alternative hypotheses

• Theropod Ancestry– Pros

• Lots of fossils– Some with feathers

• Bone morphology– Foot with 3 digits

» Embryology (birds w/5)– Sholder joint similarity

» Facilitates wings held at sides• Eggs in nest structure

– Cons• Theropod adapted for running (how

could flyer and runner share ancestry?

• Feathers? (Old argument)– Theropod fossils – yes – Used for insulation

» Exapted for flight.

• Thecodont Ancestry– Pros

• Tree dwellers– Glider forms– In the trees

• “More parsimonious argument that flight feathers evolved from gliding stabilizers rather than insulation”

– Cons• Fossil Evidence is missing

Form and Function

Feathers

• Most conspicuous integumental derivative

• Keratin

• Function– Flight– Heat Conservation

• Reduced convective and evaporative heat loss

• Increased insulation

Feather Development

• Development triggered by an interaction b/w epidermis and dermal mesenchyme

• Formation of dermal papilla (placode)

• Mitotic divisions in a collar zone of the stratum germinativum near the base of the papilla form a crown of barbs

• Covered by a horny sheath of epidermis

Lizard scales

Scaleless hen

Bird scales

Feather Development• As development proceeds:

– Differential cell division on one side of the papilla• Timing of expression of two proteins: Shh & Bmp2

– These cells form a shaft away from the body

• carrying the barbs that are formed in the collar

– The base of the feather recedes into the skin • Accompanied by layers of epithelial cells• Feather follicle

– Degeneration of epidermal sheath

Feather morphogenesis

• Movie

Morphology of a Feather

Morphology of a feather (cont)

Morphology of a feather (cont)

• Major Types:– Contour

• Insul., Flight• Vanes symmetrical• Vanes asymmetrical

– Semiplumes and • Rachis > barbs

– Down• Rachis < barbs• Insul.• Adult down• Natal down (lost)• Powder down

– Grooming– waterproofing

– Bristles• Little or no vane

– Filoplume• Monitor pennaceous

feathors• Attached to sensory

corpuscles

Plumulaceous

Pennaceous

Contour feathers

• Wings

Contour feathers

• Tail

Semiplume

• ostrich

Downnatal

adult

powder

Filoplume

Bristles

• Whip-poor-will

Cross-section of feather follicle

1. Barb ridges of epithelial

2. Surrounding dermal core of connective tissue

3. Space of the follicle

4. Epithelial tissue of follicle

5. Associated musculature

Melanins

Carotenoids

Porphyrins

Structural colors