Re: Bird (Dinosaur?) vision

[Dann Pigdon <dannj@alphalink.com.au>]

Dino Guy Ralph wrote:
> 
> Regarding the alleged inability of birds to see nonmoving items, this seems
> absurd to me, especially in light of the fact that of all creatures birds
> possess perhaps the best visual acuity on the planet, but I would be happy
> to peruse evidence that supports such a claim.

Apparently night birds like owls that have a lot of rod cells in their
retina but few cones (if any) can detect prey only if it moves or makes
a sound. I suspect diurnal birds don't rely completely on movement
though - otherwise why do budgies have such a fascination with mirrors?
And seed-eating birds certainly don't wait for their prey to 'make a
move'.

A study using chicken hatchlings {Jones 2001 "Does occasional movement
make pecking devices more attractive to domestic chicks?" British
Poultry Science (2001) 42: 43?50} found that there was no significant
increase in the chance of a chick pecking at a moving object than a
static one. In fact, they were more likely to peck at the static
objects, especially if they had prior experience and recognised them.

-- 
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Dann Pigdon
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://heretichides.ravencommunity.net/
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