Wingspan is not size
A wingspan is the widest a thing ever gets, held in a pose it only adopts while moving. It is the right number for a runway and the wrong one for a doorway, and knowing which question you are asking decides which figure you want.
What a span actually measures
A span is a distance between two extremities held apart in a pose. It is not a body dimension. A condor folded on a ledge is a bird about a metre long; the same bird in flight measures 3.2 m tip to tip. Nothing about the animal changed except its arrangement.
That makes span an odd kind of figure. It is the right number for anything to do with moving through space, which is why aviation uses it and why it is the figure quoted for every large flier in the catalogue. It is the wrong number for anything to do with how big a thing is as an object, which is most of what people mean when they ask about size.
The Andean condor, and the largest span of any land bird
The condor's 3.2 m is the widest of any living land bird. It is also very nearly the shoulder height of an African elephant, which is a comparison that lands well and says nothing useful about the bird, because a condor weighs about fifteen kilograms and an elephant several tonnes.
The catalogue puts the condor against an American bison at 1.75 m shoulder height, which is a ratio of 1.83 between a span and a height. The two numbers are both correct and they are not the same kind of fact, and the page says so.
Wandering albatross: 3.11 m, tip to tip. No living bird spreads wider. The span is the whole point of the animal, because it is what allows hours of gliding without a wingbeat, using the wind gradient above open water rather than muscle.
Quetzalcoatlus, where the span is the story
The largest flying animal known carries a stated span of 10.5 m. That is longer than a modern London double-decker bus, and it is a genuinely staggering figure. Standing on the ground, folded, the same animal was roughly the height of a giraffe.
Both of those facts matter and they describe different things. Quetzalcoatlus at 10.5 m against a wandering albatross at 3.11 m gives 3.38, which is a like-for-like comparison of two spans and therefore clean. The same span against a polar bear at 2.5 m is a span against a body length, ratio 4.2, and that one needs the caveat carried alongside it.
Rays, where the span is the body
Manta rays are the interesting middle case. A giant manta at 5 m is measured across the wings, tip to tip, and those wings are not limbs held out in a pose. They are pectoral fins fused into the body. The animal cannot fold them away.
So for a ray the span is also a body dimension, which makes it a better-behaved figure than a bird's. It still is not a length, though: a manta measured nose to tail is considerably shorter than it is wide. Against a white rhinoceros at 3.7 m, which is a head-and-body length, the ratio of 1.35 compares a width to a length. The ray is wider than the rhino is long.
Aircraft, where both numbers are published
Aviation is the one field that solves this problem properly, by publishing both figures and being explicit about which is which. An Airbus A380 is 72.72 m long and 79.75 m across. Airports size their gates on the span, because that is the constraint. Runway length depends on other things entirely.
The catalogue treats the side view and the plan view of the A380 as two objects, and both are quoted on the same 72.72 m: the distance from nose to tail. The plan view changes the outline you see, not the figure being judged. That is worth knowing before you read the plan view set against a 341 m rotor diameter, because a rotor diameter is a span and a fuselage length is not. The two numbers are comparable as numbers, but they do not describe the same kind of reach, and the page says so.
The turbine, which is all span
That 341 m figure is worth pausing on. It is the rotor diameter of the largest offshore turbine built, meaning the circle a blade tip sweeps. It is not the height of the tower, which is a separate and smaller number.
A rotor diameter is a span in the purest sense: a distance across nothing, describing the space the machine needs rather than the material it is made of. The blade tip travels that circle at speeds that would be measured in hundreds of kilometres an hour, and almost all of the 341 m is air.
When a span is the right figure
Three tests decide it.
- Is the span fixed? A ray's is. A bird's is not, though it is repeatable if the wings are fully extended. A pterosaur's is a reconstruction of a fully extended pose.
- Is the question about clearance? If you want to know whether a thing fits through a gap, gets a gate at an airport or needs a bigger hangar, the span is the only number that matters.
- Is the other side of the comparison also a span? Span against span is honest. Span against height or length works arithmetically and needs saying out loud.
The last one is the test most published comparisons fail. A wingspan next to a body height makes for a striking picture and an incoherent claim, and the striking picture is usually why it was published. Stating both conventions costs one sentence and turns the same comparison into something a reader can actually use.