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Owl Vision and Convergence

 
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owlpages
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Joined: 13 Jan 2004
Posts: 438
Location: Australia

PostPosted: Fri Jul 21, 2006 5:03 pm    Post subject: Owl Vision and Convergence Reply with quote

I have just received and interesting inquiry about owl vision, which lead me to some further questions of my own:

As we know, owls' eyes are "fixed" in their sockets, so they can only look forward. Does this mean their eyes can not converge when close to an object? If this is the case, would they suffer diplopia (double vision) for objects that are close to their face?

Also, does anyone know if all owl species have a fovea on the retina (an area of higher concentration of light sensitive cells).
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Jester



Joined: 09 Jun 2004
Posts: 403
Location: sunny aberdeen by the sea

PostPosted: Fri Jul 21, 2006 6:04 pm    Post subject: Reply with quote

This is just some ramblings from my own experience with Jester so probably not very scientific Laughing

his eyesight is very poor close up which is why everything that goes near to his face ends up being "nibbled" to see if it is food or not. however i have noticed him also looking at things more to one side of his face. i know he often looks round the side of his box in the aviary with one eye whilst the other eye is still open but only 1" from the wooben box.

perhaps they are more able to ignore the image from one eye when things are too close which might also explain why if i put food down in front of him he sometimes misses or fumbles about as one eye alone doesnt "rangefind" very well

i have no idea about the fovea so cant help there
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pepperpot



Joined: 22 Jun 2007
Posts: 2

PostPosted: Sun Jul 15, 2007 4:27 am    Post subject: Reply with quote

This is something I am interested in to find out also. My understanding is that owls cannot see close up, if I put my hand in front of my owls eyes and wave it, she cannot see it close up at all.
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paulbridges



Joined: 08 Nov 2008
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PostPosted: Thu Jan 15, 2009 8:21 am    Post subject: Reply with quote

This same question occurred to me while preparing a program on owls. On this face of it, it doesn't make sense. Not being an owl myself, I can offer these items as clues...
1. Owls close their eyes right before seizing prey, presumably to protect them, but possibly also because they are not of great use that close. Also a researcher I know says his owls sometimes appear to be "clumsy" with near objects.
2. One of my textbooks says near vision falls off anywhere from 1 to 6 feet (as I recall) depending on the species.
3. Unlike Terns and other birds that may have 2 or more fovea per retina, owls don't appear to have this, as indicated by my texts that show a single fovea that is usually high on the back side of the retina.
4. One website that shows a graphic image of a barn owl retina showed a "smudge" off to the side of the fovea. It seemed to me possible that this area of high number of vision cells can be used as a pseudo-fovea for near subjects to some degree, in that species at least. However if claim #2 above is based on a refractive limitation rather than fixation (convergence) related, then this seems unlikely.
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raptortrnr



Joined: 26 Sep 2007
Posts: 179

PostPosted: Thu Jan 15, 2009 10:00 am    Post subject: trained owls Reply with quote

All the owls Ive worked with had limited vision up close. they would often move their head away and side to side before deciding that what i was holding was food and going for it. that's why the bristles are so important, they use them like a cats whiskers to feel where the food it. If you touch the bristles it elicits a snap response for feeding.
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