Ornithology

What are the traits that modern birds share with Theropods (maniraptors)

• Feathers

• Bipedal

• Fused clavicle (wish bone)

• Hollow bones

• Foot and pelvis structure

• Long arms

Traits Theropods have in common with reptiles

Single occipital condyle: Where the vertebral column articulates with skull

• Birds have 1, mammals have 2

• Birds can rotate their heads farther because of this

Single middle ear bone

• Humans have 3

Similar scales

Sclerotic ring: Supports the eye, the bone inside of their eye

Lower jaw composed of several bones

• In mammals its just 1

Females heterogametic sex: egg of the female determines the sex of the offspring

• In mammals its dependent on the male

What were feathers originally developed for

• Insulation

• Communication (sexual)

• Camouflage 

How did flight evolve?

There are 3 theories 

Arboreal Model: evolved in tree dwelling species which made them glide

• Issues with this model: instruments for gliding is different from flight

Cursorial model: Flight evolved from ground dwelling species jumping for food

Wing assisted inclined running: flight evolved from runnng up steep surfaces and safely descending from tall heights 

Archaeopteryx lithographica

• One of the most important fossils ever discovered

• Lack of keel suggests reduced capacity fro flight compared to modern birds

• The asymmetrical primary feathers suggest powered flight

• Isn’t considered the direct ancestor to modern birds

Shared characteristics between archaeopteryx and reptiles

• Teeth in socket

• Many vertebrae in tail

• Unkeeled sternum

• Wing (arm) bones not fused

• Large eye orbit with sclerotic ring

Shared characteristics between archaeopteryx and birds

• Clavicles fused (furcula → wish bone

• Feathers on wing and tail

• Elongated coracoid bone 

• Curved scapula

• Primary feathers are asymmetrical

Sinornis santensis: Advances over Archaeopteryx

• Pygostyle: replaced the tail, tail feathers attached

• Reduced digits

• Strengthened pelvic girtle

• Foldable wings

• Perching foot

• Still had teeth

Cretaceous

Confucius ornis: Horned beak, no teeth

Hesperonis: 

• 13 species

• Flightless

• Toothed

• Unicinate process (happens in flighted birds) where rib flares and keeps ribs together

• Secondary loss of flight

Avian taxonomy

Kingdom: Animalia

Phylum: Chordata

Class: Aves

• 40 orders

• 250 families

• 10,700+ species

Taxonomy is not rigid

Alfred Russel Wallace

Divided the globe into major zoogeographic regions based on broad faunal patterns

Oceania (130 sp)

• Wide open oceans and continental shelves

• Order Procellariiformes → albatros and puffins

Neartic (750 sp)

• North America

• Simple vegetation, structurally simple

• Small diversity of birds

• No endemic families → many speceis here migrate to Central and South America and share taxa with these realms

• Few species eating fruit, nectar, and ground insectivores

Dominant families:

• Amberaizadaes: American sparrows

• Parulidae: Warblers

Australasian (900 sp)

• Australia 

• High diversity along the coast

• Low diversity in the desert

• Northern tip has higher diversity

• <5% is rain forests

• 70% desert

• Lots of endemism because it was floating alone for millions of years

• Emus, plain wanderers, lyre birds, scrub birds, bristle birds, magpie goose

Indomalayan (2,400 sp)

• India, Southeast Asia

• Draw line at Himalayas for different region

• Draw line at Wallaces line to Australasian, this is where 2 tectonic plates collide

• More species in the tropics

• Low endemics because of migration

• Pheasants → high diversity

• Collumidae: pigeons and doves

• Leaf bird family (endemic)

• Barbet

Paleartic (1,025 sp)

• Upper Africa (draw line at sahara), Russia, Asia

• Largest realm

• Low species diversity because large areas of vast unproductive boreal forests

• Lots of migrants

• 1 endemic family → accentors (warblers)

Afrotropical (2,300 sp)

• Subsaharan Africa, Madagascar, South Saudi Arabia Peninsula

• High diversity

• Lots of endemism that are only found in Africa

• Mesites, secretary bird, go away bird, shoebill stork

Neotropical (3,700 sp)

• Central America, South America, Caribbean

• High species diversity because South America has the largest amount of land mass in the tropical latitude

• Hummingbirds, tanagers, antbirds, fly catcher, oven bird

Why is there more species in Neotropical

• Greater variety of foods

• Greater range of prey size

• Stable climate allows for more specialization

• Greater structural habitat diversity → many available niches

• Large altitudinal range at tropical altitudes

• Influx of migrants from Neartic