Giant bird speed question!

[Juliana]

That's a great link, Dan! Thank you!!

 

[J Riff]

Well if a human skydiver reaches the top falling velocity, it's around 120 mph. The air is thinner the higher up you are. Go for 200!

 

[Abernovo]

My first job was working with birds, mainly wildfowl, but sometimes passerines and, occasionally, birds of prey. The simplest way we looked at it was kestrels are small attack helicopters (seriously, watch them hover), peregrines are fast jets, and eagles are strategic bombers (or tanks, depending upon who you're talking to and which comparative you wish to use). There is a different function in each, so a different structure, speed capability and agility.

So, temporarily forgetting 'conventional' physics for your creatures, but comparing them to creatures of our world, I'd expect a pegasus to go faster than a griffin, although a griffin might have a higher burst speed, and to have more stamina than a griffin/gryphon (which could of course be your classic Greek griffin as opposed to a Northern European one; or just a splitter who wants a different name).

If you want extra speed, but don't want to lose the size or species, then go for a magical workaround. Dragon cross griffin? Enchanted zebra pellets (a griffin' gotta eat)? Specially bred? Or just a genetic fluke?

 

[Juliana]

Thanks Aber! Some good ideas there. Right now, I'm thinking of rewriting the scene so the griffin gets them out of current Tight Spot™ and then they're on their own and change over to conventional transport. I just need to relocate them a little so they're closer to where I want them to be in the next scene... (I confess I've been a little worries about possible similarities to Sirius Black's Buckbeak escape, though I'm aware JK doesn't hold exclusive rights to flying creature escapes!)

My first job was working with birds, mainly wildfowl, but sometimes passerines and, occasionally, birds of prey. The simplest way we looked at it was kestrels are small attack helicopters (seriously, watch them hover), peregrines are fast jets, and eagles are strategic bombers (or tanks, depending upon who you're talking to and which comparative you wish to use). There is a different function in each, so a different structure, speed capability and agility.

That must have been an interesting job! We caught the birds of prey show at Warwick Castle on our UK trip in March and it was fascinating watching them fly in.

 

[DelActivisto]

Avies (birds) actually don't have lighter skeletons. While they may be hollow or smaller, they don't actually weigh less. Yes, that's right. Bird bones are actually denser, so tend to weigh the same as normal bones - so throw out any references to lightweight bird bones, or people will suspect your facts are at least 6 years out of date. (Or use alternative facts! Sorry, sorry. Can't help it. That's just so funny. *cough*) So, a griffin / gryphon is also going to need an absurdly long wingspan of roughly 40-60 feet in order to take off, assuming a good pony-sized 350 lb bird. (Those links are available upon request as soon as my post count is high enough.) The conclusion I'm drawing, then, is that bird bones are specialized merely to be smaller, amongst other specializations such as shape. So that bulky, lion like gryphon would probably be as flight worthy as, say, a broiler chicken. Sorry.

Good thing fantasy doesn't obey the laws of physics.

 

[RX-79G]

Avies (birds) actually don't have lighter skeletons. While they may be hollow or smaller, they don't actually weigh less. Yes, that's right. Bird bones are actually denser, so tend to weigh the same as normal bones - so throw out any references to lightweight bird bones, or people will suspect your facts are at least 6 years out of date.

If the bones are both denser and hollow, wouldn't that indicate they are stronger per weight, as in lighter for the same load carrying capacity?

 

[DelActivisto]

If the bones are both denser and hollow, wouldn't that indicate they are stronger per weight, as in lighter for the same load carrying capacity?

I would say that that's a fair assessment. It's like titanium vs steel. You can use less, and it's going to weigh less, AND be stronger. And I could be wrong about being able to use less titanium there - I'm no metallurgist.

But unlike the titanium example, the bird's bones are smaller and denser and weigh roughly the same as an equivalently sized animal. So actually, two bones the same size; the bird bone would, I'm guessing, weigh more.

 

[RX-79G]

I would say that that's a fair assessment. It's like titanium vs steel. You can use less, and it's going to weigh less, AND be stronger. And I could be wrong about being able to use less titanium there - I'm no metallurgist.

But unlike the titanium example, the bird's bones are smaller and denser and weigh roughly the same as an equivalently sized animal. So actually, two bones the same size; the bird bone would, I'm guessing, weigh more.

What I am getting at is when we call a load bearing structure "light", what we really mean is "light for what it does". A mammal skeleton would likely need to be heavier than a dense bird skeleton to bear the same muscular work loads.

So while individual bones might not weigh less, I rather imagine bird skeletons in general are lighter than their equivalents.

 

[DelActivisto]

What I am getting at is when we call a load bearing structure "light", what we really mean is "light for what it does". A mammal skeleton would likely need to be heavier than a dense bird skeleton to bear the same muscular work loads.

So while individual bones might not weigh less, I rather imagine bird skeletons in general are lighter than their equivalents.

Maybe, but the bird's skeletal structure should still weigh roughly the same, compared to a similarly sized animal. They are indeed smaller and hollow, but since they're denser, I don't know if calling them lighter really works. It be interesting to compare the weights between, say, a falcon and a rat, or someonthing.

 

[Ihe]

Or pigeon and squirrel.

 

[RX-79G]

These two creatures both weigh around 170 lbs. I think they would make interesting comparisons of different tissues to understand where the mass is invested.

 

[Vaz]

Clearly photoshopped, nobody has a shadow that cool looking.

 

[DelActivisto]

I can post links now:

Bone density and the lightweight skeletons of birds | Proceedings of the Royal Society of London B: Biological Sciences

The skeletons of birds are universally described as lightweight as a result of selection for minimizing the energy required for flight. From a functional perspective, the weight (mass) of an animal relative to its lift-generating surfaces is a key determinant of the metabolic cost of flight. The evolution of birds has been characterized by many weight-saving adaptations that are reflected in bone shape, many of which strengthen and stiffen the skeleton. Although largely unstudied in birds, the material properties of bone tissue can also contribute to bone strength and stiffness. In this study, I calculated the density of the cranium, humerus and femur in passerine birds, rodents and bats by measuring bone mass and volume using helium displacement. I found that, on average, these bones are densest in birds, followed closely by bats. As bone density increases, so do bone stiffness and strength. Both of these optimization criteria are used in the design of strong and stiff, but lightweight, manmade airframes. By analogy, increased bone density in birds and bats may reflect adaptations for maximizing bone strength and stiffness while minimizing bone mass and volume. These data suggest that both bone shape and the material properties of bone tissue have played important roles in the evolution of flight. They also reconcile the conundrum of how bird skeletons can appear to be thin and delicate, yet contribute just as much to total body mass as do the skeletons of terrestrial mammals.

 

[HareBrain]

These two creatures both weigh around 170 lbs.

That's a very impressive bird, but I think a misleading photo. Wikipedia gives the body length of Argentavis as 4 feet -- even assuming that excludes head and tail, that man must be less than five feet tall, and so can't weigh 170lb. I'd guess 120lb or so. The bird itself is estimated to weigh about 155lb, so that narrows the gap a bit, but it's still looking like the bird isn't as strangely light as might seem.

 

[RX-79G]

That's a very impressive bird, but I think a misleading photo. Wikipedia gives the body length of Argentavis as 4 feet -- even assuming that excludes head and tail, that man must be less than five feet tall, and so can't weigh 170lb. I'd guess 120lb or so. The bird itself is estimated to weigh about 155lb, so that narrows the gap a bit, but it's still looking like the bird isn't as strangely light as might seem.

Even if you make the guy 2 or 3 heads higher, the contrast is still enormous if the bird is at the max end of the 150-175 lbs.

 

[HareBrain]

True. There's definitely quite a bit of weight reduction going on somewhere (just not to the extent suggested by the photo), and it would be interesting to know where. Even feathers aren't weightless.

 

[DelActivisto]

It would be interesting to calculate the weight of something like a gryphon/griffin. From drawings, it looks like people usually place them as about the same size as a lion or somewhat larger. And a lion weighs between about 350-550 pounds. That's pretty hefty! But you can tell, from looking at a lion, that they are quite muscular and dense. So I wonder what the ideal weight of a flying large animal would be. There are large birds in our fossil record, such as the elephant bird, but it was flightless. The largest flying bird was the Argentavis, as mentioned above.

It might be fun just thinking about it - actually mentioning the weight of the creature in writing may not be that useful.

 

[Culhwch]

I can post links now:

Bone density and the lightweight skeletons of birds | Proceedings of the Royal Society of London B: Biological Sciences

I haven't read the entire article, but the excerpt doesn't seem to be saying that a bird would weigh the same as a similar sized animal, but rather that their bone to total mass ratio is equivalent.

I think anyone who has had a large bird of prey on their arm would attest that their weight is surprisingly minimal for their size. I had the opportunity to have a barn owl perch on my hand once - not a small bird at all, but crazy light.

 

[HareBrain]

I think anyone who has had a large bird of prey on their arm

Or their head! I once had a great grey owl land on mine during a birds of prey display (it apparently couldn't be arsed to fly a metre further to the glove of the handler standing behind me) and that, too, was lighter than its size would suggest. Thankfully.

 

[DelActivisto]

I haven't read the entire article, but the excerpt doesn't seem to be saying that a bird would weigh the same as a similar sized animal, but rather that their bone to total mass ratio is equivalent.

I think anyone who has had a large bird of prey on their arm would attest that their weight is surprisingly minimal for their size. I had the opportunity to have a barn owl perch on my hand once - not a small bird at all, but crazy light.

I don't really have a good answer, other than that bird skeletons evolved a little differently... light skeletons, one way or another, are better. So a lot of that shed weight is probably coming from a more efficiently arranged bone structure.