Comparative Anatomy:Head and Neck

There are so many inter­est­ing com­po­nents to a bird that I can devote an entire post to just the head and neck.

The brain is very dif­fer­ent than mam­malian brains. There are homo­lo­gus struc­tures but over­all appear­ance is very different.

Birds have rele­tively large optic lobes and rel­a­tively small olfac­tory lobes which may reflect the rel­a­tive  impor­tance of vision and rel­a­tively poor sense of smell in some birds.

Birds eyes have incred­i­ble vari­abil­ity in size, loca­tion and spe­cific func­tion depend­ing on the type of bird. For exam­ple. Owls are preda­tors and need good depth per­cep­tion so they have eyes in the front of their head like humans. This allows for stereo­scopic vision and bet­ter depth per­cep­tion. Birds that could be con­sid­ered prey species such as par­rots and passer­ines have eyes on the sides of their head. This improves periph­eral vision so they can watch for preda­tors. For great arti­cle on avian eye anatomy and how this affects vision for dif­fer­ent species, please see:

Lets move on to bird beaks/bills. The beak is a more com­plex struc­ture than peo­ple real­ize. The beak has the outer ker­atin layer that is the aspect that we see.This layer is sim­i­lar to our fin­ger nails. Under this is a layer of con­nec­tive tis­sue, blood ves­sels and nerves and then bone. There is the upper beak with an under­ly­ing max­il­lary bone and a lower beak with an under­ly­ing mandibu­lar bone. As a vet, I have seen my share of beak avul­sions. This means that due to some trauma, the upper beak or or lower beak (or both) have been torn off. It is some­times hard for peo­ple to under­stand why this doesnt grow back since they know they have seen the beak tip grow when bro­ken. The rea­son is that the tip of the beak is the end of the karatin layer and the ker­atin layer is regen­er­a­tive. As long as the base of the ker­atin layer near the cere (fleshy aspect near the nos­trils) has not been dam­aged, the outer sur­face of beak will grow out (just like your fin­ger­nails). How­ever, once there is bone involve­ment, there is per­ma­nent dam­age and then this is a more seri­ous situation.

Other inter­est­ing anatomy facts on birds: They have a cleft palate –an open­ing called choana–that con­nects to their sinuses and nos­trils. There tra­chea is made of com­plete car­ti­lage­nous rings so the tra­chea does not eas­ily col­lapse. They do not have an epiglot­tis to cover the glottis–opening to the tra­chea. Unfor­tu­nately this makes inhala­tion of seeds a true con­cern. Bird tongues have a bone to aid their move­ment and manip­u­la­tion of food. They have a less devel­oped sense of taste than humans but they have addi­tional touch recepters. Birds do have ears but they do not have pin­nae or those outer flaps of ears that we asso­ciate ears. The ears are hid­den by the feath­ers on the side of their heads.

Wow, I can keep going on bird anatomy but it is quite exhausting…so I think I will stop here for now. I think next week will have to be a small mam­mal blog week just for some­thing dif­fer­ent  :)

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