Avian Natural History Week 1

Why are birds essential in Earth’s biosphere

high motility leads to interactions among many ecosystems, move materials and energy (important consumers in aquatic plants and animals), provide service to other organisms (especially pollination and seed dispersal), serve as ecosystem engineers (e.g through burrowing and excavation of tree cavaties)

Traits common to all birds

feathers, modified forelimbs=wings, bipedal, beaks/bills, lack teeth, homeothermic endotherms, muscular gizzards (stomach), large-yolked eggs develop outside body, large brains and acute senses

Traits common to most birds

hollow long bones, keeled sternum, fused clavicles (wish bone), fused pelvic girdle

Traits shared with other reptiles

Single occipital condyle, single middle ear bone, lower jaw bones per side, ankles between multiple tarsi, B-keratin in epidermis, scales on legs, heterogametic females, red blood cells have nucleis

Class Aves

All living modern birds, their common ancestor, and all its descendents

What gave rise to the bird diversity we see today?

Diversification of modern birds occurred after the C-Pg extinction, second around 32 mya from the radiation of flowering plants

Why are modern bird relationships still under revision?

Traits to determine relationships be homologous, choice of species or traits to build evolutionary choice of species or traits to build evolutionary trees affect relationships in trees, conserved traits help define a group, many avian traits are highly malleable

conserved traits

shared by all members of a group

convergent traits

common problems yield common solutions

Where are bird found on earth?

Variation in environmental conditions lead to adaptation and diversity

Endemic

found no where else

Cosmopolitian

Found everywhere

Adaptive radiation

Many closely related species filling slightly different niches in the same geographic area