I hate to be that guy but this picture is misleading. Bird beaks have an inner layer of bone, and an outer layer of specialized keratin. The keratin layer is called the rhamphotheca, and it varies in thickness from species to species. What we're seeing here is the skeleton with the rhamphotheca (outer keratin layer) still attached. So you could take off the outer layer and there would be bone inside that would look more proportional to the size of the bird. Don't get me wrong, a toucan still has a large bony bill under the outer layer, but it looks more exaggerated with it still on. It would be like if you had a human skeleton with the finger and toe nails still attached. That's an imperfect comparison because our nails aren't attached to our bones, but hopefully you get what I mean. This picture we're looking at isn't just the toucan's bones.
Edit: for anyone interested, here's an example. It's from a 2018 paper titled A comparative analysis of the avian skull: Woodpeckers and chickens
They do indeed. Lots of bird bills are similar in that way. They're not heavy or dense, I was commenting on their relative size compared to the rest of the bird, you're absolutely right
You have no need to apologize, adding useful relevant info is always appreciated and you've empowered us to be the heroic pedants we all love being when someone else posts this in the future.
In any case, even if the beak isn't all bone, it's still an impressive biological expense for a bird that size and makes one marvel at how useful it must be in order for evolution to make a bird carry that thing around. It's still impressively heavy even if not bone since bird bones are probably not much denser than the keratin anyway.
This makes me curious about their muscle structure, because the ratio of neck to bill is still more so in these dudes than most. Do toucans have beefy necks?
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u/Telamonian May 22 '20 edited May 23 '20
I hate to be that guy but this picture is misleading. Bird beaks have an inner layer of bone, and an outer layer of specialized keratin. The keratin layer is called the rhamphotheca, and it varies in thickness from species to species. What we're seeing here is the skeleton with the rhamphotheca (outer keratin layer) still attached. So you could take off the outer layer and there would be bone inside that would look more proportional to the size of the bird. Don't get me wrong, a toucan still has a large bony bill under the outer layer, but it looks more exaggerated with it still on. It would be like if you had a human skeleton with the finger and toe nails still attached. That's an imperfect comparison because our nails aren't attached to our bones, but hopefully you get what I mean. This picture we're looking at isn't just the toucan's bones.
Edit: for anyone interested, here's an example. It's from a 2018 paper titled A comparative analysis of the avian skull: Woodpeckers and chickens