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Episode 10: Heaviest Flying Bird Statistics Inaccurate

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999983.  Mon May 27, 2013 11:19 pm Reply with quote

My bird resources tell me that the Mute Swan's heaviest members have weighed up to 33lb, while the Kori Bustard's average weight is about 30lb and the heaviest members have been 44lbs or better. So, by both average and heaviest individuals, the Kori Bustard is likely the heaviest living species of flying bird. The Great Bustard also has an average weight of about 30lb and its heaviest individuals can be upwards of 40lbs.

A quite interesting fact is that the largest flying bird in history was Argentavis magnificens, or Giant Teratorn, weighing 150-170lbs and having a wingspan of 26 feet! It likely required a wind speed of 40kph to get airborne.

One of it's nearest living relatives is also one of the current largest flying birds: the Andean Condor weighs upwards of 34lbs and has a longer wingspan (10ft) than the Mute Swan (8ft), Kori Bustard (8ft), or Great Bustard (9ft)

Sadurian Mike
1000027.  Tue May 28, 2013 5:04 am Reply with quote

mysta02 wrote:
My bird resources tell me that the Mute Swan's heaviest members have weighed up to 33lb,

I have 51lb, which puts it back in the heaviest category..

Source: Wood, Gerald L., The Guinness Book of Animal Facts and Feats (1983)

1000066.  Tue May 28, 2013 6:16 am Reply with quote

Welcome mysta02 - we'd be interested in your sources :-)

Sadurian Mike
1000110.  Tue May 28, 2013 7:20 am Reply with quote

I believe cherry or orange is traditional for swan.

1000169.  Tue May 28, 2013 10:35 am Reply with quote

Sadurian Mike wrote:

I have 51lb, which puts it back in the heaviest category..

It is true that a single oversized bird weighed that much, but it likely couldn't fly due to it's immense size. The Kori Bustard regularly grows up to 44lbs and can certainly fly. Reports of Koris of 51, 75, and 88lbs have also been reported, but never verified.

Source: Wood, Gerald (1983). The Guinness Book of Animal Facts and Feats.
Source: CRC Handbook of Avian Body Masses by John B. Dunning Jr.

1000172.  Tue May 28, 2013 10:41 am Reply with quote

Jenny wrote:
Welcome mysta02 - we'd be interested in your sources :-)

Hi, most of my information came from two books:

David M. Bird, PhD. The Bird Almanac
Jason A. Mobley. Birds of the World Series

I also confirmed these numbers on Wikipedia and checked it's sources, as well.

I did a study of bird flight a number of years ago, so I had a chart listing various birds' weights and wingspans that I'd put together.

Sadurian Mike
1000225.  Tue May 28, 2013 2:48 pm Reply with quote

mysta02 wrote:
It is true that a single oversized bird weighed that much, but it likely couldn't fly due to it's immense size.

So then, a mute swan maximum measured weight is not the 33lb that you initially quoted? If a single bird could reach such a huge weight, why not the others?

'Likely' couldn't fly, by the way, is supposition.

Unverified weights of other birds are also not acceptable. Unless you will also accept that I once saw a 70lb sparrow smoking a pipe.

1000255.  Tue May 28, 2013 4:26 pm Reply with quote

Ok, "scientists, based on evidence I'm completely unfamiliar with, but is true, nonetheless, believe that such a large bird with it's aerodynamics, wing load, muscle size, and body weight would be unable to get itself airborne."

My unverified weights were for interest-sake only. They were reported weights by laypersons and not officially weighed by scientists, hence my stating of 44lbs as a standard maximum weight of a flying Kori Bustard, rather than an unverified 88lbs.

In all experiments, outliers are expected, but when calculating the mean of a set of data, they are but one data point and don't affect the outcome of the data in any significant way.

We could say, "the heaviest, living, possibly flight-capable bird ever verified was a Mute Swan, weighing in at 51lbs", but saying that Mute Swans are the heaviest living, flying birds is simply inaccurate when we look at all the data. The average weight of a male Kori Bustard (30lb) is 5lbs heavier than the average weight of a male Mute Swan (25lb).

1000274.  Tue May 28, 2013 5:35 pm Reply with quote

I think this is one of those issues where dividing lines can be drawn up according to how you read the data.

The 1983 Gerald Wood fact says that a Mute Swan which weighed 51lb "may have briefly lost the power of flight due to its extreme weight". This suggests two things, either the author couldn't be sure that the bird couldn't fly at it's heaviest, or was only "briefly" unable to fly, which could mean that it could have been able to fly while over 44lb.

With regards to the Kori Bustard, the point made by the sources quoted say that 44lb is the verified heaviest weight, but that higher weights have been reported which are either unverified or from unreliable sources. Unfortunately, what this means is that there may be a possibility that the Kori Bustard had members which weighed more than 44lb, and perhaps even more than 51lb, but there is no verified, reliable source to prove this.

Similarly, the Great Bustard specimen has been verified at 46lb, but there have also been unverified and unreliable reports of much heavier individuals.

As such, what we can say for absolute certain is that the heaviest verified flying bird was a Mute Swan, though there are question marks on whether it could have flown at that weight.

The Mute Swan that claims the record is abnormally heavy for it's species, and by the extrapolation of average and top end of average weight, either of the two Bustards could each have individuals which are heavier than 51lb, but we've not had a verified specimen to show this.

I say put all three in my back garden and let my cat decide :)

Alfred E Neuman
1000341.  Wed May 29, 2013 3:50 am Reply with quote

Sadurian Mike wrote:
'Likely' couldn't fly, by the way, is supposition.

It does not so much fly as...plummet.

1000360.  Wed May 29, 2013 6:12 am Reply with quote

How interesting to see all this discussion when at face value you think it would be a very straightforward question!

Thank you mysta for providing your sources.

Alfred E Neuman
1000411.  Wed May 29, 2013 7:46 am Reply with quote

Around here it's fairly well accepted that kori bustards are the heaviest flying birds, but I notice that the Kruger National Park's website thinks they're the heaviest birds in Africa. Given that the the same website reckons that ostriches can be up to 135kg, I'd say they need to edit that entry.

I think I'm going to have to go and feed up (and weigh) some kori bustards so that we can prove their claim to being the heaviest flying birds.

Of course that will mean finding them first. They are quite impressive birds but I haven't seen them in the wild very often, but those I have seen were pretty near where I'm living at the moment*. I wonder if they'll stand still on the scale, or whether I'd need to make them inert somehow. And if it's inert, how do you prove that it could fly? On the other hand, inert-ness could be useful if we were to combine this thread with the BBQ one.

* Other than the ones I saw in Botswana a few years back.

1151103.  Sat Sep 26, 2015 6:19 pm Reply with quote

Hi people,
My Q is: If the pull of the earth's gravity affects lift off then what is the heaviest a bird can be to fly? I read somewhere that the heavier a bird gets the more muscle it must have to get air borne and thence the heavier it becomes again, etc etc making it a catch 22 situation.
What is the limit on this planet?

Kim :)

1151142.  Sun Sep 27, 2015 7:09 am Reply with quote

Lift increases with the square of airspeed - if the bird is heavier it just needs to run/fall faster to get airborne. There are no "fundamental" limits here, so the question has no specific answer.

Once airborne it needs to be able to sustain an airspeed such that lift equals weight (to fly straight and level) or equals roughly 1.4 times its weight to manoeuvre & land safely. To sustain airspeed requires thrust to equal drag (aka "wind resistance"). A badly-designed low-speed aero-vehicle has a cruising drag number that might be as high as a tenth of its weight - most birds are much better than this (probably between 15:1 and 20:1, although long-range birds like albatrosses can probably achieve over 60:1 when configured for cruising flight).

So you're looking for birds to have muscles that can achieve better than 1/10th of bodu weight for flight. Given than they need to achieve well over 100% body weight just to walk on the ground I suggest that this isn't a fundamental limitation either, so again there is no specific answer to the question.


Alfred E Neuman
1151200.  Sun Sep 27, 2015 3:47 pm Reply with quote

According to Proffessor Katsufumi Sato of the University of Tokyo, about 40kg.


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