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?
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...
...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).
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
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.