Thorondor's Rescue of Maedhros - Realistic or Not? by Grundy

Chapter 1

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A bird large enough to carry two men on its back may sound fanciful. But is it actually?

Let’s start by examining the text:

Now, even as Fingon ben his bow, there flew down from the high airs Thorondor, King of Eagles, mightiest of all birds that have ever been, whose outstretched wings spanned thirty fathoms; and staying Fingon’s hand took him up, and bore him to the face of the rock where Maedhros hung…and Thorondor bore them back to Mithrim. ­– The Silmarillion

This passage actually gives us a dimension. One fathom is two yards (1.83 m), so Thorondor’s wingspan is 180 feet (=54.9 m). A good rough estimate for wingspan to body length for eagles is 2:1, so using this ratio we can ballpark Thorondor’s length at 90 feet. With these dimensions, Thorondor is larger than any living bird, and dwarfs even larger extinct species such as Haast’s Eagle, Argentavis magnificens, or Pelagornis sandersi. He would moreover be several times the size of the largest pterosaur.

That remarkable wingspan would put Thorondor in good company at modern airports. The closest aircraft analog for wingspan would be a B-52 Stratofortress, with a wingspan of 185 feet (56.4m); the best aircraft comparison for length would be a Gulfstream IV[1].

Would an eagle with such proportions be capable of flight? Most likely – it has a significantly larger wingspan than modern aircraft of similar length. A better question may be how well a bird of this size would be able to replace its feathers. Biologists have shown that feather replacement is a significant constraint on large flighted birds, as the time to grow new feathers increases proportionally to feather length[2]. (We will not consider the composition or material properties of the feathers here, or attempt to determine whether the biomechanics of Thorondor’s wings, particularly bone length and composition, would be possible.[3])

Assuming Thorondor’s feathers are in fine fettle, the next question is whether or not he would be capable of bearing two men on his back. In terms of sufficient space for two people, the answer is almost definitely ‘yes’. Even assuming that as much as ninety percent of Thorondor’s body length is taken up by his head, neck, and tail (places we can rule out for carrying of people), that still leaves ten feet (three meters). Looking at a bald eagle skeleton, an estimate of fifteen to twenty percent of the body length being suitable for bearing elves seems reasonable – this eliminates the lower back, tail, head, and neck.  That gives roughly 13.5-18 feet (4.1 – 5.5 meters). The tallest of elves will be able to comfortably fit in that space with room to spare.

However, just because there is enough space for the two elves doesn’t necessarily mean that Thorondor can bear their weight. One might be tempted to take the line that it being elves he is carrying is important, given that Fellowship of the Ring implies elves either mass significantly less than Men or that gravity affects them differently than it does Men[4].  However, the rescue of Maedhros was not the only instance of eagles rescuing people in the First Age; Beren and Luthien also got an eagle rescue, as did Huor and Hurin. Note that three of these people are Men – meaning we can conclude that even lesser eagles than Thorondor must be capable of bearing the weight of adolescent or full-grown Men.

How realistic it this? Unfortunately, this is where matters become rather murky. We have no height-weight data for any of the elves or men named as eagle passengers; we also have no information on Thorondor's weight.

We could attempt a guess. Without exception, all the men are described as tall, with Maedhros tall even for an elf. We'll assume that Maedhros is the tallest and heaviest of the five men. There is no firm estimate for his height; we know him to be in good shape and strong. (Or at least, this was the case prior to his captivity.) Basketball players may be a good comparison. The tallest basketball players to have played in the NBA[5] are 7’5”-7’7” (2.26-2.31m). Their weights range from 200-359lb (91-141kg). If we assume the upper range to be applicable to Maedhros and add a margin to account for the uncertainty about his height and density, we might guesstimate the largest eagle passenger weighed perhaps 375-400lbs. Add another 325-375lbs for Fingon, and we have Thorondor carrying an estimated 775lbs (351kg).

Is it unreasonable to expect an eagle Thorondor’s size to carry this weight? Possibly not. The extinct Haast’s Eagle preyed on large flightless birds (moa) which could weigh up to 510 lb (230 kg). Haast’s Eagle was significantly smaller than Thorondor, with a wingspan estimated to be 8.5-9.8 ft (2.6 – 3.0 m) and body mass in the 25-30 lb (11.5-14 kg) range. This means Haast’s Eagle was dealing with prey potentially many times its own weight. However, Haast’s Eagle would not have been carrying moas on its back – it would have been seizing them in its sizable talons. It is also likely that the heaviest moas would have been carried only a short distance if at all.  So would an Thorondor be able to carry such weight on its back?

Unfortunately, there are very few real-world analogues for birds bearing weight on their back. Occasionally, ill-advised humans have been known to ride ostriches. The ostrich is not a very good comparison for our purposes – not only is it flightless, its body structure and adaptation is different than an eagle. However, lacking any better examples, we will make due. Ostriches pressed into giving rides have been known to carry roughly forty to fifty percent of their body weight. If we assume the same holds true of eagles, the answer to our question would depend on the weight of Manwë’s eagles.

The weight of Manwë’s eagles is also relevant to the question of the airspeed of a laden eagle. The cruising flight speed of a bird is proportional to its body mass raised to a fractional power[6]. While a heavier eagle would be more likely to be able to carry two fully grown men, the cruising speed of that eagle will also be faster. This is somewhat concerning, given that Fingon and Maedhros are not noted to have any partiularly protective clothing (certainly not more specialized gear such as goggles, ear muffs, etc.) and that Maedhros was already in a state of shock from a field amputation. A cruising speed similar to the golden eagle (roughly 30mph) might be bearable at low altitude; faster speeds or higher altitude would likely risk injury to both elves.

And as the prompt did ask – regardless of whether or not eagles of the size described would be capable of carrying people on their backs, you would certainly not want to be standing near one when it decided to poop. With any luck, the eagles regarded Gondolin much as they would their own nests, which they keep clean. The mountain slopes around their nests, however, would have to be regarded as danger zones – anyone climbing in that vicinity would be at risk of being hit by projectile poop.

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[1] Aircraft Characteristics (October 2018) MS Excel file, https://www.faa.gov/airports/engineering/aircraft_char_database/

[2] https://www.nature.com/news/2009/090616/full/news.2009.572.html  doi:10.1038/news.2009.572

[3] If anyone is interested in doing so, https://doi.org/10.1111/j.1420-9101.2011.02449.x seems like a possible starting point.

[4] Legolas, despite being described as tall as a young tree, lithe, immensely strong is somehow light enough that when walking on snow chest-high on the Men of the company that leaves Aragorn and Boromir making a path through it by brute force, his feet made little imprint in the snow.

[5] https://en.wikipedia.org/wiki/List_of_tallest_players_in_National_Basketball_Association_history

[6] https://doi.org/10.1126/sciadv.aat4269 Sullivan, T.N., Meyers, M.A., and Arzt, E. Scaling of bird wings and feathers for efficient flight. Science Advances Vol 5 No. 1 (2019).