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[deleted] t1_jb1x76s wrote

Birds have bone marrow, just not in all of their bones.

They've some pneumatic bones which are hollow and filled with air, and actually connected to their respiratory system, through air sacs in their abdomen, giving them extremely efficient respiration which is likely an adaptation for dealing with low oxygen in flight and fluctuating air pressure etc.

Obviously the hollow bones give birds a weight advantage and their bones are also made form a tougher material than ours, so despite being light they're also extremely strong and springier - all of which is about adaptions to flight.

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Mikedc1 OP t1_jb25ym6 wrote

That's cool it seems way more complex and diverse than I thought. I thought all bones were calcium like matrices with small differences but turns out birds have some other composite

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[deleted] t1_jb2k9kb wrote

More or less the same composition but the material is denser, yet full of hollow spaces and struts. They tend to break quite jaggedly compared to mammalian bones, but are usually harder to break.

They’re totally evolved for flight.

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