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Synopsis:

Some sources seem to imply the Rüppell's (griffon) vulture (Gyps rueppelli) can see objects at a distance in excess of 10 km -- roughly three times the commonly asserted vision distance of an eagle.

What studies have been done on eyes of this species and can any experts comment on the accuracy of this assertion?

Also, do we know whether their eyes perceive a similar color range to that sensed by human photoreceptor cells?


Background

Wikipedia's List of birds by flight heights lists the flight height of Rüppell's (griffon) vulture (Gyps rueppelli) as the highest known bird flight height at 11,300 m (37,000 ft).

enter image description here

The claim appears based on this ornithology journal article [PDF] ("Collision between a Vulture and an Aircraft at an Altitude of 37,000 Feet") detailing a collision over Abijan, Ivory Coast. This is a coastal city...

Abidjan, Ivory Coast

...so can be estimated to be approximately at see level, inferring this is a height above ground (roughly).

The article adds:

Vultures use their excellent eyesight to scan the landscape below from a relatively static aerial position. Instead of flying over a larger distance, they use elevation to expand their field of vision. If they spot a meal down below, the climb has an immediate payoff.

That piqued my interest, as I came across this while trying to track down what the maximum known distance an animal could see was (per a separate discussion of fantasy vision capabilities).

Human vision is according to quantitative testing limited to "~2.6 km (1.6 miles)" [synopsis], likely varying mildly based on physiologic variability.

A Wikipedia entry on eagles ("Eagle Eye") states (citing a book on eagles as its source):

The eagle eye is among the strongest in the animal kingdom, with an eyesight estimated at 4 to 8 times stronger than that of the average human. An eagle is said to be able to spot a rabbit 3.2 km away.

The statement is a little bit tenuous on the sourcing, but impressive if reasonably accurate.

The note in the list of highest flying birds, though, makes it sound like this high-flying vulture could be able to detect faint objects at a distance of 10+ km!

That in turn suggests this bird to have perhaps the longest range vision acuity of any known species, with a vision range perhaps three times that of an eagle or more.

If so, the record for animal vision would not be "eagle eye", but rather "vulture eye".

Granted, it might also all be bunk; the internet is a very inaccurate place hence why I came here to StackExchange seeking quantitative evidence in support of this claim.

Another Ruppell's griffon vulture pick from Smithsonian

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  • $\begingroup$ Humans can't see distant objects? On a clear night with dark skies (all too rare these days) I can make out the Andromeda galaxy, 2.5 million light years away. If you want something that doesn't produce its own light, Saturn at 1.2 billion km is easily visible. On Earth, I can see individual trees on mountains 20 km or more away, and on one of those rare clear days, can see Mt Shasta from the summit of Mt Rose (near Reno), about 250 km. I think what you really need to ask about is angular resolution... $\endgroup$ – jamesqf Jul 21 '17 at 5:55
  • $\begingroup$ I think the limitations that may have been missed due to my wording is 1) size of the of the object 2) an object that is not a light source. Your terrestrial examples are impressive and of interest, but deal with objects signficantly larger than those discussed (see MIT candleflame discussion) in this thread and attached links. Likewise Andromeda to my understanding is a somewhat different example than the one discussed here as it's much larger in relative angular vision than a distant mouse at 1 km+. Maybe you're right on the angular vision term... is that the proper terminology here? $\endgroup$ – Jason R. Mick Jul 24 '17 at 16:39
  • $\begingroup$ And how would I quantify how small a range would be implied for this vulture to improve the question? Feel free to edit my question jamesqf if you feel that putting this in angular terms would improve the clarity! $\endgroup$ – Jason R. Mick Jul 24 '17 at 16:40
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    $\begingroup$ You might ask whether this vulture has the greatest visual acuity. The problem is that you don't specify what sort of objects it sees at 10 km. Large objects, as per my examples, are no problem to see at much greater distances. A dead (since it's a vulture) critter? But what sort? The eagle can spot a rabbit; can the vulture spot a dead rabbit at greater distance? Then there's the issue of camoflage: I sometimes don't see rabbits until I almost step on them, but can track them at some distance if they're moving. $\endgroup$ – jamesqf Jul 26 '17 at 4:04
  • $\begingroup$ Thanks, when I get some time I may reword this further per your suggestions in hope of eventually getting an answer. $\endgroup$ – Jason R. Mick Aug 2 '17 at 16:39

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