Lecture 9

Front 1

Photoreceptors of Avian Retina

Back 1

Translate light into nervous impulses

1. rods: black & white vision

2. Cones: color vision

3. double cones: color vision, perhaps polarization sensitivity

Front 2

Diurnal Birds' Cones Special Properties

Back 2

Colored Oil Droplets

Carotenoid pigments

protect against damaging UV light

enhance the contrast of objects against different backgrounds (yellow against blue background and red against green background)

Front 3

What do Avian Retina Lack?

Back 3

No blood vessels

Which means prevents shadows & light scattering.(Less visual interference)

Front 4

Avian Retina: Pecten

Back 4

Pecten

Highly vascular structure projects from the retina

nutrients & oxygen diffuse from it, to retinal cells (rods/cones)

MAY be unique Avian characteristic (unknown if all birds have it)

Front 5

Avian Colour Perception

Back 5

Photopigments (Photoreceptor proteins in retina) absorb light (different photopigments - see certain colours)

European Starlings: 4 photopigments (vs human's 3) - four different outputs

Can see multiple hues when we only see one

Front 6

Avian Foveae

Back 6

Foveae: Concave depressions of high cone density (area with Highest concentration of sensory cells)

Horizontal streak (central area): Across retina, high concentration of sensory cells, with a fovea too at each end

Most birds have multiple fovea

Front 7

Sharpness of Vision depends on

Back 7

Concentration of Cones in "horizontal streak" area

Front 8

Diurnal Birds of Prey Cone Density

Back 8

Very high cone density in Foveae

may be as high as 65,000 per square millimeter

Front 9

Avian Ear Structure vs Mammalian Ear

Back 9

Similar acoustical efficiency, mechanics

Simpler structure

No pinna

Only stapes (columella)

Front 10

External Acoustic Meatus

Back 10

Short canal to tympanic membrane

covered by special feathers that do not obstruct sound transmission

Front 11

Semicircular canals

Back 11

Important for Birds for FLIGHT

regulate the balance and spatial orientation

can reorient automatically with respect to gravity (even without sight)

Front 12

Brain and semicircular canals size vs Flight Performance

Back 12

Increase Flight Performance

Increase Semicircular canal size and cerebellum

Front 13

How do Birds Hear

(like Mammals)

Back 13

1) Sound waves cause the tympanic membrane to vibrate.

2) Vibration of the eardrum causes vibration of the stapes.

3) Vibration of the stapes causes vibration of the oval window (a membrane at the entrance to the cochlea).

4) Vibration of the oval window causes pressure waves in the fluid in the cochlea.

5) These pressure waves cause movement of the basilar membrane (on which hair cells, or papilla, are located).

6) As the basilar membrane 'vibrates', the hair cells are 'deflected' or bent by contact with the tectorial membrane & this generates nervous impulses.

7) Impulses travel to the avian brain, stimulate nerve cells in the brain, & the bird 'hears.'

Front 14

Avian Hearing Ranges

Back 14

1-4 kHz = best/normal

10-12 KHz = Some

Determining frequency contrast or sound gaps = like humans

Fainter sounds and general freq ranges = humans better

Front 15

Avian Olfaction

Back 15

Small size of olfactory bulbs in most birds (relative to brain size)

But do probably use smell in their daily routine

Generally olfaction like some mammals

(some passerines equal ability to rats/rabbits0

Front 16

Birds with large olfactory bulbs

Back 16

vultures, Kiwis, and tube-nosed seabirds

Front 17

Avian 3 Sleep Stages

Back 17

Sleep=maintain neural circuits

Slow wave (SWF): One side of brain in sleep stage, other alert "one eyed' keeping watch while other birds in REM (feature of birds)

Intermediate

REM: short and frequent bouts (between SWF)

Front 18

Avian Brain

Back 18

~ 6-10 x the size of similarly sized reptiles

Hyperpallium = Mammalian cerelbral cortex = learning and intelligence center = advanced cognitive abilities (vs old view they don't)

Large Optic lobes = visual input important

Large cerebellum = balance and coordination importance

optic lobes and cerebellum = for flight

Front 19

Caching Behavious

Back 19

Enlarged hippocampus = Large memory

Crows and jays
nuthatches: Many pine seeds stashed in thousands of different hiding places

tits and chickadees

lesion hippocampus = continue hiding seeds but can't re-find them

Front 20

Irene Pepperberg and Alex (Parrot) Experiment

Back 20

parrots are capable of complex reasoning and communication

Thinking not just repeating vocabulary

English vocalizations to identify, request, refuse, or comment on object's identity and features