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20 Cards in this Set
- Front
- Back
Photoreceptors of Avian Retina |
Translate light into nervous impulses 1. rods: black & white vision 2. Cones: color vision 3. double cones: color vision, perhaps polarization sensitivity |
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Diurnal Birds' Cones Special Properties |
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) |
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What do Avian Retina Lack? |
No blood vessels Which means prevents shadows & light scattering.(Less visual interference) |
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Avian Retina: Pecten |
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) |
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Avian Colour Perception |
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 |
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Avian Foveae |
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 |
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Sharpness of Vision depends on |
Concentration of Cones in "horizontal streak" area |
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Diurnal Birds of Prey Cone Density |
Very high cone density in Foveae may be as high as 65,000 per square millimeter |
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Avian Ear Structure vs Mammalian Ear |
Similar acoustical efficiency, mechanics Simpler structure No pinna Only stapes (columella) |
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External Acoustic Meatus |
Short canal to tympanic membrane covered by special feathers that do not obstruct sound transmission |
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Semicircular canals |
Important for Birds for FLIGHT regulate the balance and spatial orientation can reorient automatically with respect to gravity (even without sight) |
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Brain and semicircular canals size vs Flight Performance |
Increase Flight Performance Increase Semicircular canal size and cerebellum |
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How do Birds Hear (like Mammals) |
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.' |
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Avian Hearing Ranges |
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 |
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Avian Olfaction |
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 |
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Birds with large olfactory bulbs |
vultures, Kiwis, and tube-nosed seabirds |
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Avian 3 Sleep Stages |
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) |
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Avian Brain |
~ 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 |
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Caching Behavious |
Enlarged hippocampus = Large memory Crows and jays tits and chickadees lesion hippocampus = continue hiding seeds but can't re-find them |
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Irene Pepperberg and Alex (Parrot) Experiment |
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 |