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I get some interesting emails.

A theory of species:

The question of the identity of the 'African Swallow' referred to by King Arthur in Chapman et al (1975) is still unresolved.

Personally, I feel it is unlikely to have been the South African Cliff-swallow Hirundo spilodera as European knowledge of geography would not have spread as far in King Arthur's time. It seems likely that only species breeding in West Africa or Ethiopia would be known to Europeans and perhaps Ethiopia, land of Prester John (who I'm sure would have been a close personal friend of King Arthur) is perhaps the best candidate.

I would propose that either Red-chested Swallow Hirundo lucida (which breeds in West Africa and western Ethiopia) or Ethiopian Swallow Hirundo aethiopica (which breeds in the Sahel and Ethiopia) and which both closely resemble European Swallow, are two likely candidates, although the widespread Lesser Striped Swallow Hirundo abyssinica is another possibility.

The problem highlights the problems of specifically identifying species from manuscripts and documents dating from pre-Linnean times, when there was no standard terminology.

— Mike Pennington, Unst, Shetland

A theory of swoggles:

I have no doubts that your research ("Estimating the Airspeed Velocity of an Unladen Swallow") is thoughtful and thorough, but isn't it rather like the Ultimate Answer in Hitchhiker's Guide? That is, have we forgotten the original question? Namely, how did coconuts get to Medieval England?

Frankly, I have my own theory involving swallows, coconuts and crop circles. As you know, crop circles have appeared in England in great numbers. A flock of swallows can be called a "swoggle" (borrowing from "swoop" and "gaggle"). In the case of East African swallows, this would be a "hornswoggle."

If a large enough swoggle were to circle a coconut grove as they gain altitude for their migration, is is possible that the flight could produce a tornado effect, thus lifting the coconuts off the ground and making them airborne? Then, as the swoggle begins its migration, the coconuts could be swept along in the swoggle's slipstream.

Upon arriving at their migration home in England, the swoggle naturally would circle a landing area, presumably a cultivated field where there would be ample food to replenish the swoggle members‚ energy after a long flight. As they land, the slipstream would disappear, and the coconuts would begin falling to the ground. The weight of the milk-laden coconuts then would pummel the underlying crop, crushing it in a pattern that would match the landing flight of the swoggle.

It‚s a theory. I have no facts to support it.

Respectfully,

— Charles Wright

A theory of coconuts:

Far be it from me to pointout any lapses in the logical flow, but I feel the following theories must also be factored:

1. We must consider the displacement potential of a fully developed coconut - could the swallow, whatever specie, have ridden the coconut from tropical climes, via one of the prevailing currents, to the shores of southwestern England (given that the "historical" Arthur was most likely from Cornwal, in south western England, this can't be discounted out of hand).
    
2. Do we know, from any archeological evidence, that it was actually a coconut being used, and not a malformed walnut suffering from a botanical gigantism?
    
3. It was only postulated, orginally, that the coconut may have been carried (or vice-versa!) by a swallow. Given our more modern knowledge of the migratory practices of the creatures of the world, can we discount the "swallow theory" and put forth a candidate known to migrate vast distances - the Monarch Butterfly.
    
4. Could the coconut be, in fact, the remains of a locally grown variety, in place since before plate tectonics moved England into the Temperate zone?
    
5. Alien Coconut Abduction and Relocation

— Gary Cooper

A theory of agri-ethics:

I am in full agreement with Mr. Cooper's assertion. In addition to considering a second study regarding the load bearing capacity of the European Swallow (Hirundo rustica), given the non-relevant migratory pattern of the South African Swallow (Hirundo spilodera), I believe the scientific community also needs to consider the antecedent to the fully-laden swallow flight, that being a question of the biometric capacity of a swallow to grasp a coconut by the husk.

This link of a picture of Hirundo rustica [link now obsolete] shows with great definition the diminutive nature of the species claw. As such, there are potentially two critical biometric questions.

1. EXTENTION CAPACITY: Does the fully extended Hirundo rustica claw have the capacity to gain adequate grip upon the husk.
    
2. STRENGTH: If so, does the Hirundo rustica have the grip strength to maintain its grip on the husk during extended migratory flight?

Potentially, even more significant antecedents involves the bird's motivation and ethics? Why would a Hirundo rustica attempt to carry a coconut to England? From an agri-ethics standpoint, would the bird transplant non-native fauna to a foreign land? Lest we be accused of being armchair ornithological psycologists — or even worse pop-culture agri-ethicists — I recommend we seek out specialists in these area before proceeding.

— William Koleszar

A theory of continents:

I wish to thank you for your wonderful work in answering the swallow question...

However, you fail to address an inherent problem with both the African and the European Swallow theory i.e.: that it is believed that the coconut was indigenous to Brazil and Paraguay..... we should therefore be looking at a South American Swallow....unless of course the European Swallow can be assumed to have flown to South America then grabbed a coconut and returned to Europe....Considering the air distance from London, England to Rio de Janeiro, Brazil is about 5770 miles (roughly 232 hours or 9.67 days in the air at 24 mph unladdened!) A migratory African Swallow would have a slightly longer journey even if one left from Albania (closest African land to Europe) of about 5938 miles.

Now, can you determine the ASV of a laddened swallow? According to my web research the average weight of a fruit of a tall palm is about 8 kg. However I can find no average diameter.

Grasping the coconut by the husk may effect the weight and size as well since usually the "nut" actually has a smooth surface surrounding the "husk" in its natural form...therefore the swallow may be carrying slightly less than the 8 kg. but the air resistance of the coconut will increase if carried by the "husk"

Assuming a 8 kg weight gain (from the coconut grasped by the husk) and ignoring the drag and wind resistance from such an object...what does this do to the equation?

Would this force the Swallow (of whatever national origin) to increase the number of wing flaps to the quoted 43? Perhaps it was assumed that 43 was the needed number of wing flaps for a LADDENED Swallow ....the additional 8 k causing the increase to maintain air speed velocity.

Certainly this will also drop the ASV to far less than 24 miles an hour. The "return trip" lasting significantly longer than the unladdened 232 hours.

Also, how does one compute the "drag" of the husked coconut, assuming it is carried below the Swallow in flight?

Finally, how long can a sparrow go without food?

Thanks for your continued research! I hope these facts and questions will spur you on to a more complete and accurate answer....

Else I will have to taunt you a second time!

— Ld Rupert the Persistent

 

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